The game will retain the basic fundamentals of its predecessors, though new to the series is the Inner Frame, seen in more modern MG/RG/PG kits. Gunpla will be built on these frames. The frames not only act as a base for the builds but also determines the abilities and expected roles in teams, from granting buffs to emphasizing focus in certain areas like melee combat. In addition, players will be able to replace parts with ones fallen off of enemy units and stored in an inventory menu where they can be swapped out for at any time, allowing for a "real-time customization battle" or stored in a Recovery Box. Builder Parts will also return with an increased cap of 8 parts. Also new is the ability to change the music that plays in particular for your Gunpla.
The team aspect of the game has also been reworked into a new 3V3 team battle where opposing teams must race against the clock fulfilling objectives and gaining points under a time limit.
Unlike previous games, EX Skills and Optional Weaponry are now treated as a single entity and have to be unlocked by leveling up, either through defeating enemies or opening containers. Each body part of the Gunpla may have multiple weapons and abilities but only one of them can be assigned at a time.
The game takes place around Gunbre High School, a prestigious Gunpla Battle school in Japan, You (default name: Kyosuke) are a second-year transfer student looking to improve your already impressive talents. Upon arriving, you encounter your old childhood friend, Yui, whom you used to enjoy building Gunpla with until she moved away. You find out she is now a third-year student and welcomes you to the school. After meeting with your homeroom teacher, Shia Aida, you're introduced to your classmates. Ms. Aida suggests a demonstration, pairing you up with class representative Iori Koura. Teaching you the controls of the school's Gunpla Battle system fires up Iori and she lets loose, leading to the two battling and defeating a Perfect Grade RX-78-2 Gundam. Afterwards, Ms. Aida allows the class to spend the day Gunpla Battling, though she seems worried...
Later that day, Iori takes the player character on a tour of the school, they find themselves encountering Yui defending a student from Shogo Moria, a member of the Student Council-backed team "Shield of Laplace". The two are drawn into a fight, which they handily win with Yui by their side. Humiliated, Shogo runs off with a threat of revenge. Hiding in the 08th Club's room, Yui and Iori tell the player character of how the Student Council took over the school, when two powerful Gunpla Battlers, Daisuke Sena and Yuki Shina, defeated the entire Council at the time. Daisuke used his parents' influence to push people around and, when Yuki was elected President and Daisuki Vice President, the two enacted strict rules with a "might makes right" mentality. However, their talks are stopped when Ryoko Otori, Student Council Secretary and leader of Shield of Laplace burst in, claiming the trio were plotting insurrection against the Council. As it turns out, Shogo ran to her after his loss. Not wanting to take this laying down, the trio battled the two in another battle and proved victorious. Shogo ran off in a huff, though Ryoko acted quite strange, hinting that things weren't over yet.
Knowing things wouldn't be the same anymore, the trio opted to form their own team to take back their school. However, their plotting was interrupted by a sneeze - turns out there was an actual club member in the 08th Club room - Marika Sakurai, a shy first year student who sought to get better at Gunpla building, but found herself frustrated at the strict rules. With Marika's help, she teaches the trio about Gunpla Frames and lets them use a special machine to train offline, away from the School Council's sight. She also gives them their team name - Side 0.
After this, the game separates into numerous paths between Yui, Iori, Marika, Ryoko, energetic yet scatterbrained Chinatsu, school idol Shion and the mysterious Recoco. With the exception of Recoco, these events have you bonding with a certain girl and winning their affections as you rise up in the ranks. In the process, you face off against three major characters - Shogo, whose Gunpla part thievery is halted after defeating him; Shimon Sakaki, leader of the Golden Cosmos team, who blackmailed Marika into aiding him and is proven that throwing money at Gunpla is not the same as enjoying them; and Masumi Shiro, leader of Airbrush of Zeta, who is told that his obsessing over painting will not improve his skills.
Ultimately, after confronting and defeating Ryoko and Sena, Side 0 comes up against Yuki, who has been waiting for this encounter for the longest time. It's revealed that Sena ended up planning all of these encounters just so those of Side 0 would finally reach Yuki. In the amazing showdown that follows, Yuki is initially defeated, but recovers and creates two copies of himself. Ultimately, they are defeated and you and the girl of choice vanquish Yuki. In his shock, Yuki reveals that, when they were children, the player character had defeated them, shattering his sheltered illusion of power. However, he is told off for his new way of thinking and learns to love Gunpla as it should be. Yuki, then, dissolves the Student Council and let a new group rebuild everything.
At the end, the player character becomes the new President and, in an attempt to get away from everyone else, he and his chosen girl run off for more Gunpla action.
In addition to new Gunpla, the Gunpla from the previous games were confirmed to all return, aside from SD Gundams, which will not be in this game. Similar to the original two games, new Gunpla will also be added in future updates following its launch. Interestingly, though all previous Gunpla are set to return, they will not all be there at the very start, instead being brought in over numerous updates as to not overwhelm players. Similar to Gundam Breaker 2, duplicate parts are automatically sold as there are no low or high quality parts to be collected.
- New Gundam Breaker is the first in the Gundam Breaker series to be released worldwide
- While Gundam Breaker 3 featured an English translation, that version was only released in Asian territories with no proper localization plans for it.
- New Gundam Breaker is the first localized Gundam game to be released for the PC.
- When New Gundam Breaker was released, players and critics heavily criticized the game for its broken game mechanics. Of note, Japanese video game magazine Famitsu gave it a low grade of 27 (where the other games in the franchise were in the middle to upper 30s) while Amazon USA and Japan both brought its star ranking down to 1 1/2 stars before Amazon was forced to deactivate the rating system. The backlash forced Bandai Namco to release a series of patches for the game in order to fix it.