Kotomine Kirei is the son of Risei Kotomine, a priest managing the Cathedral Church during the Fifth Holy Grail War. He serves as the supervisor of the Holy Grail War and an agent of the Church. Trained in Eight Extremes Fist, he possesses exceptional combat prowess, rivaled only by few Masters like Kayneth in the Fourth War. Surprisingly, he uses healing magic learned to care for his wife, though painfully applied. Despite a tragic life, Kirei chooses villainy, instigated but not forced by Archer in Fate/Zero. He has a clear moral sense yet embodies pure evil by nature, unique among humans in the Fate series, constantly pursuing answers to his twisted desires through evil acts.