|Japanese name:||仁賀 征爾|
|Appears in:||Fate/Prototype: Fragments of Blue and Silver|
|Character type:||Human, Master|
|Master rank:||Third (Thrones)|
He has shoulder-length black.
Seiji is killed by Assassin's Zabaniya: Delusional Poison Body just after summoning her, after her allure drives him to kiss her.
Seiji is inexperienced as a magus.