A 7th-grader attending Seiho Academy. An only child, his family owns the shop Iori Models, and he's been a Gunpla fan from a young age. Both his building technique and his Gundam knowledge put many adults to shame. However, he's a poor Gunpla Battler with a long record of washing out in the first round. It's confirmed that Sei is the creator of a customized GAT-X105 Strike Gundam model, the GAT-X105SEI Build Strike Gundam: A model focusing on mobility, it specializes in quick, hit-and-run attacks. Unit: GAT-X105SEI Build Strike Gundam