Seiichiro is a boy in the third grade of Seiyo Academy. He greatly admires Amu, and in the first episode of the anime, she rescued him from two boys that were assaulting him. He was very grateful, and even asked Amu for her autograph. But she just told him he was blocking her way as well and walked off. His obsession with her appears to have developed since that interaction and now calls her "Amu-senpai". He even began to write an anthology of "Hinamori-senpai's wonderful sayings", shown in Episode 24. During Episode 2, his heart's egg was one of the first of the victims of Yuu Nikaidou.