Wild with a hearty personality, Koga has great self-confidence and always thinks of himself as the best. A self proclaimed "wolf," he snaps at everyone no matter who they are. Since he has a keen nose, he dislikes things that have a strong smell.

He has a corgi named Leon, who is good friends with second year Subaru Akehoshi's pet dog, Daikichi. He is somewhat hostile toward third year Rei Sakuma and calls him "vampire bastard," but as it turns out, Rei is good at making Koga do his bidding. A member of the unit UNDEAD.