Graham overall is a career soldier, always looking for the next challenge. He's fearless, confident, prideful, stubborn, honorable, a romantic, and later a devout believer in Bushido (ancient Japanese samurai philosophy and martial arts). Being one of the best MS pilots on Earth, he became bored with life as there was little to challenge his talents. After the appearance of Celestial Being and squaring off with the Gundams, he self-admitted that their appearance gave him a reason to live again and it became his obsession to defeat Celestial Being with the pride of a Flag Fighter. As such, he stubbornly piloted all Flag mobile suits without considering the GN-X series. It was only after the Flag became obsolete that he relented to piloting a GN-X,GNX-704T/AC Ahead Sakigake.
After the events of AD 2307 (Season 1), Graham never completely recovered mentally and physically from his encounters with CB, especially with Gundam Meister Setsuna F. Seiei. He treated his previous battles as a defeat and can only find a personal sense of closure by defeating CB. Graham studied the ways of Bushido to further develop himself as a warrior (influenced by Homer Katagiri). He then wore an old samurai mask to cover the scarred tissue over his face as a constant reminder of his defeat so that he may draw strength from it in battle.
By AD 2312, (Season 2), he was a licensed ESF soldier under the alias, Mr. Bushido. He was granted complete autonomy over any mission he chose. Because his only interest was in Setsuna/00, he often stayed at a distance until he eventually challenged Setsuna to settle his personal score to restore his honor. Graham wanted to die in glorious battle, but Setsuna denied him the satisfaction, instead telling Graham to let go of the past and fight for the future. That battle resulted in Graham putting aside his past transgressions and returning to his old self.
By AD 2314, Graham discarded his mask and Mr. Bushido identity. He had let go of his grudges against the Gundams and realized his misguided obsession was wrong. He returned to the ESF Army as a more confident leader, now more willing to work with a team. Graham was given command of the new Sol Brave Squadron. Graham now understands the importance of mutual understanding and the need to live for the future.