Mamiya Keiichi (間宮 圭一 Mamiya Keiichi?) second year student in the Ishigami school Sumo club. He took over as captain after the loss to Inter-High Preliminaries
- Mamiya Keiichi vs Mitsuhashi Kei
- His blood type is A.
- He uses glasses outside the ring, but when he fights, he uses soft contact lenses.
- He likes idols.
- His family owns a flower shop, as whown when Mitsuhashi Kei bought carnation for Mother's Day in Otake 7. He visited before facing each other in Inter-High Preliminaries.