Rikichi is the youngest member of Zero Squadron, and is the only one who did not fight in the original Black Rebellion (that's not to say he didn't try). The Black Knights rejected his enlistment attempt on the grounds that he was too young.
Rikichi's early childhood prior to the Britannian occupation was fairly typical; his grandfather tried to install pride in Japan in him, but at this age Rikichi didn't really pay much attention. After the Britannian invasion, things took a turn for the worse. His parents did become honorary Britannians, but were still stepped on (one time their home was broken into and they couldn't report it because they knew the police wouldn't care.) After this, Rikichi started to develop an intense hatred of Britannians, which was only fueled by the Devastation. He was able to join Zero Squadron largely on talent, but does not fit in with the rest of the team, who view him as an annoyance (the only other teammate as disliked as he is is Lilliana Vergammon, a blood thirsty psychopath who transitioned to the Black Knights largely out of her desire to kill people). However, only his wingmate Charmelle is aware that his hatred is deeper than he lets on, and even she is unaware of the full extent.