|School||Fujou High School|
Ōimachi is a student at Fujou High School when the tournament game school competing for Roka's Bag, he was cast as reserve contestant, because Kenji had been knocked unconscious after being Takao's zipper bust shot.
He then became part of the Allies of Kazama Gang.
- Just like other characters' in D-Fragments series, their names are reference to railway stations in Japan. His name is derived from Ōimachi Station.
- Throughout series run his face hasn't been seen at all, because he always comes up with his back.