team-yuetsu

yuetsu

(…) Egged on by Archer, Kirei Kotomine, having awakened to the pleasures of depravity, leaves morality behind and satisfies his dark appetites. (…)  His unusual Master/Servant relationship with Archer could be said to be the show’s highlight. 

Ufotable on Team Archer.  Fate/Zero Blu-ray Disc Box II

Nothing else to say.