In Mobile Suit Crossbone Gundam, Tobia is a somewhat naïve and very hot-headed teenager who often instinctively rushes into dangerous situations. It is later recognized that rather than recklessness, his instincts are in fact his unique Newtype ability that allows him to get to the core of problems quickly through decisive actions. Tobia harbors much respect for his mentor Kincade Nau and Berah Rorah, and would go to great lengths to protect Bernadette Briett, even if it is eventually revealed that she is the daughter of Crux Dogatie, the ruthless leader of their enemy Jupiter Empire.
By the time of Mobile Suit Crossbone Gundam: Ghost, Tobia, now going by the alias Curtis Rothko, is more laid back and very friendly even to strangers. Though he tends to apologize a lot much to the confusion of Font Baud. He has taken up an alias and keeps his true relationship with Belle a secret that rather than a guardian, he is in fact her father. When it comes to battles, he's still as determined as ever and years of experience has made him into a skilled veteran who takes all battles very seriously.
Another thing to note is that though he's blind, he doesn't talk about it all that much nor does he treat it as an impairment. This is demonstrated when he still chooses to pilot and even when facing against the EMS-TC04 Desphys he asks for help instead of blaming his blindness for hampering his abilities.
Curtis as a father also gains an overprotective side towards Belle, such as when he warns Font that had he made a pass on Belle on Jupiter he would be executed. Numerous times he whispers into Font's ear, in a delightfully jest manner, that he better cease with the passes anyway for his own good. When Font later elopes with Belle, Curtis is seen torn between hypothetically executing Font or marrying his daughter to him.
Ten years have passed since the armed resistance of the aristocratic fraction, the Crossbone Vanguard, is defeated in the events of Mobile Suit Gundam F91. Tobia Arronax is an exchange student on board the spaceship Smashion to Jupiter from Earth. He becomes wrapped up in the Jupiter War during a surprise attack by a group of space pirates who call themselves the Crossbone Vanguard. In danger, he decides to hijack a EMS-06 Batalla to put up a fight against Kincade Nau in the XM-X1 Crossbone Gundam X-1, but is soon routed. Tobia is then spared by Kincade, and the latter leads him to poison gas containers on board the ship, unearthing a conspiracy of the Jupiter Empire. Tobia is then assaulted by Professor Karas, who is revealed to be an agent of the Jupiter Empire disguised as a teacher for Tobia. He is saved by Kincade.
Kincade takes Tobia to board the pirate ship, Mother Vanguard and is convinced by its captain, Berah Ronah, to join them. The pirate group's true identity is revealed to be a guerrilla group resisting the secret faction within Jupiter, the Jupiter Empire, who intends to invade Earth. Determined to help bring an end to the war, Tobia becomes a pilot of the Crossbone Vanguard, and despite often being quick-tempered and letting his emotions get the best of him in battles, his skills in piloting mobile suits continue to improve with Kincade as his mentor.
The first mobile suit designated as his own is a captured EMS-10 Pez Batalla that has been repainted with an eye to identify it as a member of the Crossbone Vanguard. With his awakening Newtype abilities, Tobia uses the Pez Batalla to destroy an EMA-04 Elefante on the Moon that has threatened to destroy the Crossbone Vanguard's fighting force. However, Tobia and his Pez Batalla are later captured and taken aboard the Jupitris 9, the flagship of the Jupiter Empire en route to Earth. After being forced into participating in a gladiator-style battle against XM-X2 Crossbone Gundam X-2, piloted by Rosemary Raspberry of the Death Gale Squadron, while armed with only a hand pistol, Tobia manages to escape the Jupitris 9 in the X-2's core fighter back to Mother Vanguard.
At some point on their journey back to Earth, Tobia assists to defend Mother Vanguard from Jovian forces near a resource asteroid but his Pez Batalla crashes onto the asteroid. He is taken in by an orphaned young lady Twink Stella Laberadu, who is the sole remaining inhabitant of the asteroid. Tobia learns that Twink's parents have perished on the planet, and she has to engage in perpetual menial labor for the Jupiter Empire in exchange for food. Sympathetic towards Twink's plight, despite her scheming to take him hostage to exchange for the freeing of the asteroid from the Jovians' control, Tobia promises to bring her back to Earth when the war is over after he and Kincade dispatch the Jovian troops.
Upon reaching Earth, Tobia is recruited and held up by Sherindon Ronah, a cousin of Berah who takes great interest in Newtypes. After being held aboard her mothership Eos Nyx, Tobia watches helplessly as Sherindon schemes to stop Berah from continuing the fight against the Jupiter Empire by exposing the Mother Vanguard's position to the Earth Federation so Berah and her crew would be incarcerated. However, the defected Zabine Chareux sneaks onto the scene and fires at the Earth Federation forces in his XM-X2 Crossbone Gundam X-2 Kai, provoking them while framing Mother Vanguard as the culprit. Returning fire, the Earth Federation forces led by Harrison Madin, with feigned assistance from the Jupiter Empire forces in the area, eventually overwhelm Mother Vanguard and sink it. Enraged by Sherindon's betrayal and abandonment of Berah, Tobia steals the new XM-X3 Crossbone Gundam X-3 aboard Eos Nyx and heads to the battlefield. After a brief fight where he quickly dispatches Jupiter Empire guards in his X-3, he is able to recover Bernadette held aboard a EMA-06 Elegolea set on AI pilot. Afterwards, he also saves Berah from the sinking Mother Vanguard, but not before witnessing the apparent death of Kincade in the hands of Zabine. Tobia descends to Earth with his X-3 aboard an escape pod launched from Mother Vanguard with Bernadette and Berah and goes into hiding in a farmer's house, hoping to continue his fight against Jupiter Empire. It is on Earth when he first experiences gravity, and during a search for parts to repair the damaged X-3, he is surprised by Earthnoids' ability to walk some 12 km just to reach another town. They are soon discovered and held captive by the Death Gale Squadron led by Giri Gadeucca Aspis, but are set free in a scuffle caused by the farmer's monkey pet piloting a mobile worker. Able to activate the previously unresponsive X-3 with a lucky punch from the farmer, Tobia pilots the X-3 and engages the Death Gale Squardron. He defeats Roseberry and Burns, but is caught off guard and strangled by Giri. Before he is about to receive a fatal hit however, Kincade comes to the rescue and swiftly takes down Giri, saving Tobia.
After a brief reunion with Kincade, Tobia follows the crew of Crossbone Vanguard to capture an Earth Federation base with old rockets to propel their mobile suits directly back to space for the final battle against Crux and his Jovian invasion force. While preparing to launch, he writes a letter to Sherindon, telling her about his epiphany that the Newtypes are not necessarily a superior evolution, but rather an adaptation to changing surroundings.
Having escaped the Earth's atmosphere, Tobia and the Crossbone Vanguard join in the fight between the Jupiter Empire and the Earth Federation, the latter of which is losing due to being blitzed by surprise. However, the Jupiter Empire forces are themselves taken by surprise when the Crossbone Vanguard forces attack directly from Earth's orbit underneath the Jupitris 9, and Tobia is able to destroy Jupitris 9 and the masses of nuclear weapons on board, forcing Crux to launch all of his 9 EMA-10 Divinidads, each piloted by a clone of his, to counterattack.
Tobia soon runs into his former teacher, professor Karas, who pilots the EMA-07 Nautilus. Angered by his former teacher's sinister survival-of-the-fittest philosophy with little regard for human lives, Tobia goes on a rampage in his overdriven X-3 and quickly destroys the Nautilus and Karas' escort forces. In his dying words, Karas praises Tobia for being a fine student as he has surpassed and defeated his own teacher, and even destroys an incoming Jovian mobile suit to cover Tobia from damage before his eventual death. After defeating his teacher, Tobia senses that most of the remaining Divinidads fighting in the battlefield do not harbor hatred as would a human, and quickly deduces that the real Crux is onboard somewhere else. At that moment, he spots an escape pod ejecting from Jupitris 9 and heading for reentry to Earth, which contains the Divinidad with the real Crux onboard. Tobia quickly follows suit. On their descent to Earth, Tobia ruptures the escape pod to reveal Crux's final Divinidad, but his X-3 is knocked away from the escape pod, and he uses his X-3's beam shield as a reentry vehicle.
Tobia and Crux settle down in an ocean body on Earth and continue their skirmish. Tobia queries for the reason of Crux's hatred for Earth and humanity, to which Crux responds that rather than conquering Earth for Jovians, his plan is simply to destroy all lives on Earth as a personal vendetta against Earth Federation's continued belittlement and intimidation of Jupiter. As a recipient of a political marriage set up by the Earth Federation, Crux's hatred is further twisted by his inability to face the fact that his arranged wife (i.e. Bernadette's mother) is in fact a kind and sensible person, which makes him feel even more miserable.
After a tough battle, Tobia disarms the nuclear missiles aboard the Divinidad with his X-3's Murasame Blaster, then rams his arms' I-field generators into Divinidad's firing large mega beam cannon, causing the Divinidad to explode and killing Crux. Tobia escapes in his core fighter moments before the explosion, but the X-3 is destroyed by the explosion.
With Crux Dogatie defeated, Berah and Kincade take back their original identities and retire from active fighting, entrusting leadership of the Crossbone Vanguard and the pilot designation of the XM-X1 Crossbone Gundam X-1 Kai to Tobia, where he later upgrades it to the XM-X1 Crossbone Gundam X-1 Kai Kai "Skull Heart" which bears a similar motif to that of Tobia's destroyed XM-X3 Crossbone Gundam X-3.
After the events of Mobile Suit Crossbone Gundam, Tobia continues to run the Crossbone Vanguard under the disguised front of a transport company named "Black Row Transport".
Tobia has a brief encounter with Harrison Madin during a mission to retrieve letters sent by Kincade on Earth from a cargo ship.
Some time later, Tobia is engaged by a mysterious old man named Grey Stoke, who wants to hire the Crossbone Vanguard to recover "Amuro Ray". Together they raid a Jupiter Empire's research facility, where a bio-clone made from Amuro Ray's core fighter combat data is being inserted as the AI pilot of a prototype mobile suit Amakusa. After a tough battle, Tobia and Grey are able to defeat the Amuro clone.
Three years after the war against the Jupiter Empire, Tobia and the Crossbone Vanguard once again cross swords with the Jovians. He rescues Europa Dogatie, the step-mother of Tetenith Dogatie who has escaped from the Jupiter Empire, from pursuing mobile suit forces from Jupiter. He is initially met with hostility by the Jovian until she relents after seeing Tetenith alive. Europa mentions that he closely resembles a Jupiter Empire soldier named Curtis Rothko, Europa's lover who is killed in a skirmish against pirates a few years ago.
Europa further explains that the Jupiter Empire, under the joint leadership of Callisto's Light and Callisto's Shadow, is once again planning to attack Earth. This time, they are scheming to destroy the Earth Federation's capital and other important cities with a colony laser named Divine Punishment to be fired directly from Jupiter's orbit. She informs Tobia that they only have two weeks until the colony laser is fired, and they have to act fast. Given the short time, they would need a spacecraft equipped with Minovsky Drive originally used by the Mother Vanguard in order to get to Jupiter on time to stop the attack, but the Mother Vanguard has already been destroyed in the previous war.
Tobia then remembers a project taken by SNRI that experimented with miniaturizing the Minovsky Drive. Seeing it as the only hope, the Crossbone Vanguard quickly heads to the SNRI facility on the moon that is developing the experimental mobile suit: the F99 Record Breaker, and there they meet up with SNRI officials, including Myra Migelle and Minoru Suzuki, the latter being the lead test pilot of the facility.
The SNRI officials are initially hesitant on lending the Record Breakers but eventually agrees. Suddenly, Jovian forces led by Callisto's Shadow's mobile suit Cornix start attacking the facility, swiftly destroying the 3 Record Breakers, their data and spare parts, which makes it impossible to use the Record Breakers to reach Jupiter in time. Tobia attempts to fight Callisto's Shadow but is instead nearly killed by the mysterious pilot, with his X-1 "Skull heart" badly damaged as a result.
With the Record Breakers unusable, the Crossbone Vanguard is in a huge pinch without a way to reach Jupiter in time. Fortunately, SNRI presents them a footage of an Anaheim Electronics experiment involving Minovsky Drive, codenamed "Project Icarus". The footage shows "Project Icarus" entering the atmosphere and is thought to have perished. However, Tobia sees that it survives instead, using the "Wings of Light" the Drive creates as a heat shield for atmospheric reentry. Now with hopes that Jupiter can be reached in time, Minoru warns that the mission to Jupiter will be suicidal, and thus a team of skilled pilots will have to be assembled. Seeing "Project Icarus" as the only remaining option, Tobia takes Europa, Minoru and Mitchell Derek Nar with him to Earth in order to search for the whereabouts of the experimental machine, and recruit skilled pilots that can help fight the Jovians.
After arriving on Earth, Tobia first attempts to recruit his former mentor, Kincade Nau to join the suicide mission. However, after hearing that the former pirate is now living peacefully with his wife and is expecting a second child, he chooses not to recruit him due to the slim chance of survival of participating in the mission. He then goes to recruit Burns Gernsback, one of his former adversaries from Jupiter Empire whom he befriended. Burns agrees and advises him to enlist the rest of the Death Gales Squadron.
Burns takes Tobia, Minoru, and Europa (in disguise) to a restaurant. There, Tobia meets Giri, the former leader of Death Gales Squadron and a rival of Tobia, who is now a cook. Tobia tries to enlist Giri to help the Crossbone Vanguard's mission, but Giri initially refuses, telling Tobia that he is still loyal to Jupiter Empire. Then, Europa reveals her identity to Giri and tells him that her brothers, Callisto's Light and Callisto's Shadow, are now joint presidents of the Jupiter Empire. This news greatly angers Giri who has a history with the condescending Callisto brothers. Giri is also about to warn Tobia about Europa, but not before their reunion is interrupted by Callisto's Shadow and his forces barging in and holding all of them captive.
In the initial confusion, Tobia is instantly knocked down and pinned by Giri, who claims to Callisto's Shadow that he is still a loyal soldier of the Jupiter Empire. As Callisto's Shadow gloats about his victory, it is revealed that he is able to find out their location because of Europa, insinuating that she is a spy. Europa denies being a spy, and Tobia tells her that he still trusts her. Callisto's Shadow chides both Tobia and Europa, and reveals that rather than a colluding spy, Europa is actually used as a trojan horse because the Callisto brothers can telepathically read her thoughts, even from interplanetary distance. Callisto's Shadow then orders his forces to kill Tobia and co. as he forces Europa to board their mothership Elcopty. At the brink of the moment, Giri turns onto Callisto's Shadow and attacks him, telling him that he will never serve under the Callisto brothers, and causes a scuffle. Burns and Minoru seize the moment and knocks down the soldiers holding them captive. To aid Tobia, Bernadette pilots the XM-X1 Crossbone Gundam X-1 "Patchwork" to engage enemy mobile suits. Callisto's Shadow runs away to Elcopty. Europa picks up a gun from a fallen soldier and chases after Callisto's Shadow, with Tobia tailing after her. Europa is confronted by Callisto's Shadow inside Elcopty, but Tobia arrives to break the fight. Callisto's Shadow attempts to kill both by opening the hatch of the ship and sending them falling from mid-air, but they are saved by Bernadette using the X-1 Patchwork's ABC mantle. Their fight is then interrupted by the arrival of an Earth Federation squad led by Harrison Madin.
In order to avenge against the Callisto brothers, Giri agrees to join Tobia. Also, upon reunion with Suzuki, who turns out to be his ex-coach, Harrison agrees to assist Tobia and co. on salvaging the remains of "Project Icarus". Tobia then feeds disinformation to Calisto through conversing with Europa, hoping to confuse the Callisto brothers on their search for Icarus. While Minoru and Harrison heads to the search for Icarus, Tobia proceeds to recruit the last member of Death Gales Squadron, Rosemary Raspberry, who turns out to be the test pilot of Icarus. After being promised a sizable reward, Rosemary, who is passionate about fighting, immediately agrees to join Tobia.
Having detected Callisto's Shadow's movement, Tobia and company rush to the canyon where Icarus is stranded, and discover that rather than a mobile suit, Icarus is in fact a large Minovsky Drive test bed of over 100 meters in length. It is driven into a cliff by Rosemary after failing to land on reentry. With the help of Harrison and the Earth Federation's forces, they attempt to recover the stranded craft but their operation is interrupted by the arrival of the Jupiter Empire squad led by Callisto's Shadow in his mobile suit, the Impulse Cornix. After a tough battle, Tobia manages to defeat Callisto's Shadow with the help of Minoru and Burns, but the X-1 Patchwork is heavily damaged. Fortunately, the Icarus is unscathed.
Soon after Icarus is converted into a spacecraft, Tobia and company departs Earth and steals along Harrison's F91 (in fact let loose by Harrison on purpose to strengthen the expeditionary force). The Steel 7 team is formed, with Tobia assuming the role of close-combat cover, piloting the repaired and upgraded XM-X1 Crossbone Gundam X-1 Full Cloth. Their plan is to destroy Divine Punishment with nuclear missiles to be fired from the F-90II I-type piloted by Minoru.
After a week of space flight, they reach Jupiter's atmosphere and engage the Jupiter Empire defending Divine Punishment. Before the battle begins, Tobia is given the identity and information of Curtis Rothko by Europa. She tells Tobia to use it as an alias to cover his true identity, as he would want to stay on Jupiter after the battle to help Bernadette, but his history with the Crossbone Vanguard - a longstanding enemy of the Jupiter Empire - might be burdensome.
After fierce fighting, the Steel 7 team manages the break through the Jupiter Empire's defense line, but suffers heavy losses in the hands of the 2 mobile suits piloted by Callisto's Light and Callisto's Shadow, whose consciousness is transferred into a bio-computer upon his physical death on Earth. Unable to shake off the Callisto brothers and with the firing countdown of Divine Punishment approaching, Tobia and the Steel 7 team makes a desperate attempt to complete the objective. Nuclear missiles fired from Minoru's F-90II I-type are intercepted, but suicide attack by Giri manages to alter the firing angle of Divine Punishment slightly, causing its first shot to miss Earth. In order to destroy Divine Punishment once and for all, Tobia goes on a suicidal rampage in his X-1 Full Cloth to engage the Callisto brothers in an attempt to cover Minoru's advance towards Divine Punishment. With Callisto's Shadow's mobile suit, Libertas Dextra Dictus, destroyed by Mitchell's heroics, Tobia is able to cripple Callisto's Light's mobile suit, Jurisdis Sinistra Dictus, and reaches Divine Punishment to start taking apart the internals of the colony laser. The heavily-damaged Jurisdis Sinistra Dictus catches up to the X-1 Full Cloth and they resume their death match inside the barrel of Divine Punishment moments before its next firing, and Tobia eventually emerges victorious by defeating Callisto's Light with Europa's help. After the fight, Tobia and Europa are about to be caught by the explosion of Divine Punishment, but Europa sacrifices herself to save Tobia by grabbing and swinging the X-1 Full Cloth away from the colony laser.
Tobia ultimately survives the explosion but loses his vision due to the blinding light emitted by the colony laser. He goes into hiding, changes his outlook, and reemerges 2 years later to reunite with Bernadette, who has now assumed her original identity of Tetenith Dogatie and leadership of the conglomerate as part of the remaining wealth of Crux Dogatie's Jupiter Empire, and serves as her close aide with the alias Curtis Rothko since.
The year is U.C. 0153. It has been 17 years since Steel 7 and the blind Tobia Arronax now goes by the name Curtis Rothko. At one point he conceives a daughter, Belle, with Tetenith Dogatie, though their relationship is kept a secret for unknown reasons. Strangely enough, while Curtis Rothko has clearly aged, Tetenith looks nearly exactly the same as her younger self from 17 years ago and only grows a bit taller. The reason for this is never explained. It is also revealed that prior to the start of Ghost's event, Curtis would discover the XM-X0 Crossbone Gundam Ghost in an abandoned transport belonging to the former Crossbone Vanguard, along with an extra-terrestrial bacterium living on a meteorite that would be named Angel Call. Angel Call is later stolen by Erin Schneider, a Jupiter Empire loyalist who has seen through Curtis' true identity as Tobia. Tobia would learn that Erin intends to trade Angel Call with the Zanscare Empire, which is constructing the Angel Halo in order to subdue Earthnoids.
Curtis Rothko, along with Belle who insists on coming, locates Font Baud after he accidentally stumbled upon information regarding the Angel Halo that was on the Internet. Curtis reveals that he doesn't want to get Font involved, however, due to his discovery and the opening of the file containing information on Angel Halo it means that the Zanscare Empire will stop at nothing to kill him. Thus Curtis offers Font to come with them or die here. At this point, the Zanscare Empire attacks in MW544B Sandhoges and Curtis reveals the X-0 after it brings down a fog over the battlefield.
Curtis manages to finish off the Zanscare Empire's Sandhoges quickly, with Belle commenting in front of Font that Curtis is her father, and retreats into the Mobile Suit Museum. Here he takes a breather and while Belle searches for a usable mobile suit for Font and her to escape, Curtis allows Font to ask him any question he wants. Much to his surprise, Font just wants to know about the X-0. Since he promised to answer his questions Curtis reveals that the X-0 was supposed to be delivered to the Crossbone Vanguard 20 years ago, but due to an accident, the transport ship was destroyed. Thus, the X-0 remained dormant for 20 years until Curtis found it.
With that out of the way, Belle finds a working MS-06 Zaku II though it's only there for events and has no real weaponry which isn't much of an issue since Curtis is sure he can handle all the fighting. At this point, the Zanscare Empire attacks again and Curtis meets them in the X-0. Just as he has achieved victory an unknown mobile suit appears and attacks.
Curtis is at a disadvantage and asks Font to explain what the mobile suit looks like since he can't rely on what he knows to determine how to fight it. With some pressing Curtis reveals that he fights through his hearing and his knowledge of enemy mobile weapons. However, since this one is unknown he's literally fighting blind against it. After some fighting, Font describes the mobile suit to him and Curtis realizes it's the melee specialized EMS-TC04 Desphys belonging to Thoucus (short for Thousand Custom), a group of renegade-turned-mercenaries from Jupiter. With this knowledge, thanks to Font, he's able to avoid defeat and eventually kicks a building on top of the Desphys so that they may escape before the situation grows worse.
When the Desphys breaks free and gives chase, Curtis forces the colony to open its exit under threat of being fired upon. With that out of the way, they escape to the Manzana Flor. Once they have escaped, Font is examined by the crew and the very next day Curtis meets Font and warns him to stop making passes with Belle for his own good. At this point, they receive an announcement from Tetenith Dogatie and during this time, Bell reveals in front of Font that the woman in the projected image before them is her mother.
After the speech ends and the Crossbone Vanguard is revived, Curtis is taken by surprise that all the responsibility has been passed onto him. However, he resigns himself to this and mutters about politicians, outside forces, and how peace is drifting further away. Curtis then brings Font to another room and reveals what Angel Call really is and how devastating it would be if it was used now of all times since it has no counter. Thus he employs Font as a hacker and goes on to explain in great detail on past and current events.
Curtis gets wind of Thoucus contacting the Zanscare Empire on moon's surface, and decides to ambush the Zanscare mothership to extract intel about the whereabouts of Angel Call with Font's hacking skills. It turns out that Thoucus is making a rendervous with the Golden Egg Squad commanded by Kizo, a vice admiral of the Zanscare Empire, and the latter purposely leaks this information to Serpiente Tacon to lure them into fighting with Thoucus in order to test their strength. While Curtis and the Serpiente Tacon successfully disable the Zanscare mothership to extract intel, they are ambushed by a League Militaire squad led by three black Victory Gundam piloted by the trio of the Rear Shrike Team, Tres Mares, Deux Nauga Fluss and Yi Lychee. The battle is further thrown into disarray when Thoucus emerges to engage both Serpiente Tacon and League Militaire, and eventually outmatching both factions. With the help of Font and Belle's temporary vision, Curtis singlehandedly defeats the three black Victory Gundams, but is outnumbered and cornered by Thoucus. However, Curtis is able to retreat with Font's improvised diversion with rocket boosters, while bringing along the Rear Shrike Team and the two surviving V Gundams.
Though not officially allied with the League Militaire, Curtis decides to form a temporary alliance with the Rear Shrike Team to fight against the Zanscare Empire. With the intelligence extracted from the Zanscare mothership and deciphered by Font, Curtis and co. are able to learn that Erin's trade with Zanscare Empire for Angel Call has entered a stalemate, and Erin is still in possession of the virus. They are also aware of the location and time of the upcoming round of dealing for Angel Call between Erin and the Zanscare Empire, which takes place in Jaburo on Earth. With Font's mission finished and fearing for his safety, Curtis asks Font to leave the Serpiente Tacon so that he will not get caught by the upcoming perils; however, Font refuses to leave.
From the Zanscare mothership, Curtis's team recovers a shrunken head, which turns out to be the decapitated head of a spy close to Curtis, who has risked his life to recover intelligence regarding Angel Call but is taken captive by Zanscare Empire and is later executed. He spends a brief solitary moment with the shrunken head to reminisce the old times when they would talk about a grand plan of forging 100 years of peace in the chaotic Universal Century, and is later joined by Font. He tells Font about the story, and his spy's open execution by the guillotine as the Zanscare Empire's ploy to terrorize occupied citizens and bind them into submission.
Curtis and Font are later contacted by Quo Gray, the leader of Thoucus, who has captured Side 5 and has taken Font's parents as hostages to extort the Serpiente Tacon into surrendering. Curtis and co. are given 24 hours to turn themselves in or Font's parents and some randomly-chosen innocent kids would be executed by the guillotine. Curtis attempts to calm the rattled Font and tells him not to act rashly without a plan, but Font eventually sneaks out in a Victory core fighter to try to save his parents and the other kids. Font's reckless actions, though eventually gets himself captured by Thoucus, is able to buy time for Curtis to sow his plan to retake the colony, and Curtis and Serpiente Tacon are able to arrive just in time to save Font from a pinch and defeat the Thoucus members there, while capturing Jack Friday in his EMS-TC04 Desphys.
For the upcoming mission on Earth to recover Erin and Angel Call, Curtis reorganizes the MS force onboard Manzana Flor and assigns Tres to co-pilot with Font the newly-acquired EMS-TC02 Phantom. While ostensibly claiming that Tres's piloting skills and experience can make up for Font's lack of experience as a pilot, Curtis's assignment does carry an ulterior but comical motive of trying to set up Tres and Font, so Belle does not get too cozy with Font. He also hands Font a remote control, stating that it is a detonator for self-destruction of Jack's MS, just in case Jack betrays Serpiente Tacon (the device is in fact an intercom allowing Font to communicate with Jack remotely). On the other hand, he fabricates a story to Jack that Font is an monstrous pilot who is able to take down Jack easily, hoping to put Jack in line. Before launching, he tells the crew of Serpiente Tacon to do a last-minute check on Belle's whereabouts, fearing that she might have sneaked onboard an MS.
Curtis and the rest of the MS crew descend onto Earth and enter Jaburo, where they immediately encounter fighting between Thoucus' Earth squad and the Zanscare Empire. Thoucus attempts to intercept Curtis and the Serpiente Tacon, and Curtis engages the leader of the squad, Animal Belva, in his EMS-TC-G01 Kirjarugu. With intelligence on Curtis provided by Quo, Animal is able to gain an upper hand over Curtis by using the abundance of trees in Jaburo's environment to interfere the X-0's infrared sensors, which are vital for enabling the blind Curtis's awareness of the surroundings. As they fight on and Curtis remains on the defensive, Animal tells Curtis that as a Jovian soldier, he is present at the defence of Divine Punishment (the events of Steel 7) and has suspected Curtis's identity to be Tobia Arronax, given similarities in their fighting. Suddenly, Belle appears in Deux's V Gundam and offers to lend Curtis her vision again, but is rejected by Curtis as he fears that the overuse of the abnormal power will have bad consequences. Meanwhile, Curtis is carrying out his own plan by randomly knocking into trees around the battlefield, which tricks Animal into believing that the X-0 remains disoriented, but in fact, he is clearing up the battleground of trees so that his X-0's infrared sensors can function again. When his plan is complete, he immediately reverses the tide of the battle with one decisive strike, crippling Kirjarugu and critically wounding Animal. In his dying moment, Animal finally realizes that Curtis is indeed Tobia. After the fight, Curtis reunites with Belle, and moved by her resolve, he allows her to help the cause with her special ability.
With Belle aboard his X-0, Curtis and co. catch up to Kizo, who is attempting to forcibly extract Angel Call from Erin. As they engage Kizo, Erin feeds a video recording of his dying confession to Curtis. In the video, he explains that his original intention is to trade Angel Call to Zanscare Empire to be loaded onto the Angel Halo to paralyze all Earthnoids, giving way to the Jovians to rise to prominence. However, his attempt to develop a vaccine for Angel Call was a failure, and concludes that the bacterium is beyond human control, and will eventually lead to the extinction of the entire human race. The bacterium is immune to all sorts of cure, and will only be killed by heating of 2,000 degrees Celcius for at least 56 seconds. Upon learning that the virus has no cure, the Zanscare Empire refuses to continue trading with Erin. Worse yet, Erin himself and his ship are infected by the Angel Call by accident, and he has to immerse himself in a special solvent he has developed, which can delay (but not stop) the liquefaction effects of the bacterioum. As a last act of conscience, he decides to exterminate the virus by setting off the thermonuclear reactors of scrapped MSs beneath the waters of Jaburo, which will create immense heat enough to do so. He has set a time delay to the detonation so Curtis and co. have enough time to leave the zone.
On the other hand, the Zanscare Empire decides to get rid of Erin and Angel Call by launching a thermonuclear hydrogen bomb missile, which is set to arrive momentarily. Unfortunately, Curtis is unable to stop Kizo from extracting Erin moments before the detonation, and has to order everyone else to retreat in order to avoid being destroyed by the detonation and the hydrogen bomb arriving shortly after. While Font is able to stop the milssile strike.
Having failed to stop Kizo, Curtis and his crew head to Maria City, a city established at the site of Machu Picchu, Peru, to which Kizo and Erin are transferred. There they witness the brainwashing ritual of ordinary civilians by Maria El Tomoe, and encounter Rosemary Raspberry who provokes Maria and causes a scuffle. Curtis rescues Rosemary from Zanscare snipers, and they all escape to the sewers to lose the chasing Zanscare Empire soldiers.
With Rosemary's help, Curtis and co. are able to infiltrate Kizo's secret base underneath Machu Picchu, and the crew runs into Maria El Tomoe. Though Maria agrees to bring them to Erin, Curtis is wary of her motives. His suspicion of her is confirmed when it is revealed that she is actually the wife of Kizo and she has led the crew into a trap set up by Kizo, where the infected and dying Erin is trapped in a sealed container. As Kizo gloats about being able to extract Angel Call from Erin, Curtis attempts to shoot him, but his bullets are blocked by bulletproof glass. Kizo then punctures the sealed container with his sword to release the bacterium to kill Curtis and his crew in the room, and escapes with Maria through a secret lever. Seemingly trapped in the room about to be infected by Angel Call, a Zanscare Empire soldier enters to abduct Belle on Kizo's order, but the crew seizes the moment and manage to escape the room (except Tres who is left behind) through the door from which the soldier enters. Curtis gives chase to the soldier, knocks him out and rescues Belle, but wonders why Kizo wants Belle captured.
After Curtis and the crew escapes, they have to stop the Angel Call from spreading by allowing time for it to be destroyed by the fire set off in the secret base, while fending off the assault by Thoucus, which is oblivious of the leaked bacterium and simply wants to defeat the Serpiente Tacon to extract the Angel Call. After fierce fighting, Font is able to remotely control Phantom to contain the Angel Call from leaking from the secret base, and the bacterium. Just as the crew is relieved, however, the Zanscare Empire attacks with a large force to cover for a nuclear missile launch to terminate the virus and the inhabitants of Maria City. Curtis authorizes Font to use Phantom to intercept the nuclear missile, while he and the rest of the crew defend the city from the Zanscare Empire invading force. Font succeeds in disarming the missile in a highly risky maneuver, and with the help of League Militaire, Curtis is able to repel the Zanscare Empire, saving the city and its inhabitants.
Curtis then enters into a negotiation with Hangerg Ewin, the leader of League Militaire. Not wishing to jeopardize Tetenith's efforts in dealing with Zanscare Empire for the peaceful release of the psychikers onboard the Angel Halo, Curtis refuses Hangerg's offer to ally with League Militaire to directly assault the Angel Halo. Nevertheless, he and Hangerg enter into a non-aggression pact, allowing the Serpiente Tacon to continue its quest to seek out Kizo and destroy the Angel Call.
Curtis's decision to stay neutral between League Militaire and Zanscare Empire is disagreed by Font, as the latter believes that it would be more rational and efficient for Serpiente Tacon to team up with League Militaire and take down Angel Halo by force. The two argue, and Curtis scolds Font for being apathetic for disregarding the safety of the psychikers aboard Angel Halo. Abashed and weary of battles, Font elopes with Belle in the X-0, but later comes back after an encounter with Seabook Arno, brining along some bread baked by Seabook for Curtis.
Curtis punishes Font's eloping by sending him to work in the kitchen, peeling potato skins (a tribute to his own initial experience at the Crossbone Vanguard for breaking rules). However, he admits to Font that he is actually relieved upon learning about their escape, as doing so would have kept them out of harm's way. Also, realizing that he is powerless in stopping Belle and Font bond, Curtis is humorously torn between letting the two consummate and accepting Font as his son-in-law, or executing Font. As Font returns, Curtis asks him to lend his strength to Serpiente Tacon once again in order to stop Kizo.
Curtis and his crew leave Earth in Manzana Flor to stop Kizo's plan to bring both League Militaire and Zanscare Empire into submission by threatening to attack the Angel Halo in Earth's orbit with warships infected by Angel Call. Before Curtis sorties in his XM-X0 Crossbone Gundam X-0 Full Cloth, he eats the bread baked by Seabook, and for a brief nostalgic moment in his mind, revisits his original identity of Tobia as he pledges to "Mr. Kincade" that he will do his best.
In space, Curtis and the crew attacks Kizo's fleet on course towards the Angel Halo. Despite heavy resistance by the defending force, they are able to approach the infected ships. Meanwhile, Thoucus joins in the fray, hoping to steal and monopolize Angel Call for profits. Upon reaching the ships, Curtis dispatches specially-designed heat guns to the crew to sanitize all infected ships and mobile suits in the area. Kizo appears in his custom mobile suit, the EZM-S01 Midas, and turns the tide of the battle to his favor by using the Midas Touch Flash System, which by injecting a computer virus through light-emitted signals, immobilizes most of mobile suits in the battlefield. Although the X-0 also appears paralyzed, thanks to the X-0 Full Cloth's distinctive sensory mode which does not depend on visual images, it is only partially affected by the Midas Touch Flash System and remains operational albeit with sluggish movements. Believing that the X-0 Full Cloth is incapacitated, Kizo approaches the X-0 and demands Curtis's submission to his rule, but Curtis bluntly rebuffs him and calling him out for only attempting to create a "Kingdom of Death". As Kizo goes for the killing blow, the X-0 Full Cloth retaliates and takes Kizo by surprise, and the two mobile suit engage in a fight. Maria comes to Kizo's aid in her mobile armor, the EZMA-S01 Chaosrel, and Curtis takes on both. During the fight, Curtis reveals to Kizo his secret plan to destroy all presence of Angel Call in the area by using a makeshift solar system, which he has built by exhausting all his connections and political influences. The makeshift solar system is formed by many sunlight reflectors on the space colony modules through Side 1 to Side 7, with target guidance handled by the Newtype ability of Belle and other Newtypes residing in the space colonies. As a result, most warships and mobile suits in the area that are infected by Angel Call are destroyed along with the bacterium itself.
Refusing to admit defeat, Kizo orders Maria to push one infected warship away from the heat zone of the solar system. Curtis and Kizo continue to fight as the Manzana Flor rams and latches itself onto the infected warship, and sets its course for the Sun to destroy the remaining infection, while the crew onboard evacuates. Gaining an upper hand against Kizo and Maria, Curtis manages to land a point blank shot on the Midas, and the latter is blasted away in an explosion. As Curtis reunites with Font to evacuate, however, it turns out Kizo and his Midas are still alive, and he ambushes them and slices the X-0 Full Cloth in half. Curtis manages to escape in his core fighter, but is severely wounded and knocked unconscious. Kizo takes over Manzana Flor and captures Belle and some of the main crew aboard.
Curtis is rescued and treated aboard the Thoucus' mothership, but remains unconscious until after Font defeats Kizo and rescues Belle in the subsequent and final sortie chasing the Manzana Flor. While Font successfully resets the course of Manzana Flor back to its original path towards the Sun, Curtis is informed by him via video communication that Manzana Flor has already accelerated to a very high speed away from Earth's sphere, and that the cockpit hatch of the Phantom Gundam is ruptured and cannot shelter the two of them in space, thus there is no plausible way for Font and Belle to escape back to Earth and be rescued by Curtis directly. However, Font devises a plan of return by going into hibernation with Belle in a cryogenic capsule onboard Manzana Flor to be carried by the Phantom Gundam on auto-pilot, and when they reaches Venus, the Phantom Gundam carrying the capsule would perform a programmed gravitational slingshot around Venus to return to Earth, and would then decelerate with Earth's gravitational assist to get into the Moon's orbit. The capsule would then emit an SOS signal, so that Curtis can locate the lifesaver and rescue them. Curtis promises Font and Belle that he will rescue both of them, and finally admits to Belle that he is her father.
Mobile Suit Crossbone Gundam: Dust
Having lost contact with Belle and Font as the SOS signal emitter on their cryogenic capsule malfunctions, Curtis and Tetenith decide to take turns to search for their whereabouts along the Moon's orbit and taking care of their son Nicole, while the other would go into cryogenic hibernation. However, after Tetenith hibernates, a coup d'etat takes place on Jupiter, forcing Curtis and Nicole to go into exile in Earth's orbit. Curtis is then taken hostage and imprisoned in Side 3.
- In SD G Generation DS, Tobia can be obtainable early in the game rather than in the Encore Session if the game is played on Special Mode in either UC or AU routes.