A Newtype candidate from the Flanagan Institute, Marion was a former Zeon civilian and wanted to help Professor Chlust Moses. Wanting to end the war, Marion leapt at the chance to end the war and went along with the EXAM Project. However, she gradually learned of Professor Moses' fear and hatred of Newtypes. His desire to give Oldtypes an advantage in battle, Chlust developed the EXAM System, where a Newtype would guide the pilot to victory. Being a newtype, Marion was a test subject for the system. However, during one of the test runs, an accident occurred resulting with Marion's soul becoming trapped within the EXAM System, leaving her body comatose state. As a result, anyone who pilots an EXAM System-equipped mobile suit would temporary posses Newtype powers due to Marion's presence within the system. However, she is not completely cut off in the system and on many occasions attempts to reach out to the pilots utilizing the Suit and the system. Unfortunately many of her attempts to beg pilots for help led most to going insane, save for Yuu Kajima and Nimbus Schterzen.
Understanding Marion's plight, Yuu takes her request on board as part personal mission of sorts and during the battle at California Base, Yuu defeats Nimbus' Efreet Custom, while getting the Blue Destiny Unit 1 beheaded in the process. During Yuu and Nimbus' rematch at Side 5, Yuu destroys both Blue Destiny Units 2 and 3, ending the run of the EXAM System.
Marion's fate after Blue Destiny Unit 1's and Efreet Custom's destruction is unknown, though the manga suggests that Marion was dead and had moved onto the afterlife.
Ultimately Yuu was successful in destroying all four EXAM mobile suits, and as a result of their destruction of the system, Marion awoke from her comatose state.
- Many video games (most notably the SD Gundam G-Generation series) suggest that destroying EXAM wakes Marion from her coma.