Thanatos No.4. Bears a grudge against Toneriko (this is explained fully in chapters 6-7). His mannerisms and speech are rather crude, and he has a habit of making rude hand gestures a lot (particularly towards certain people).
His rank is implied to have remained the same for about ten years, as he's shown as rank 4 in a flashback scene from the time Toneriko first joins the guild.
Sakura's weapon appears to be a pair of wrist blades he uses in hand-to-hand combat, but despite this he's never actually seen using them.
Vova
