A character from Fate/stay night. He is a priest that oversees the 5th Holy Grail War.
In Fate/stay night, Kotomine is in his mid 30's with slightly long brown hair and blank brown eyes. He wears a black bishop class priest uniform with, usually opened, dark purple cassock with golden cross. In Fate/Zero, during his younger days he was in his mid 20's, he had short brown hair and wore a lower class habit.
Kotomine is often associated with mapo tofu and this is sometimes used as a reference to him (a fan nickname for him is "Mapo Priest").
The following tags implicate this tag: kotomine_kirei_(fate/zero) and rasputin_(fate) (learn more).