Anju's sarcastic talking doll. He often tells Karin how useless she is, which usually leads to Anju punishing him. The other dolls in Anju's room also talk and have their own personalities, but "Boogie-kun" is her favorite. Boogie-Kun is actually a murderers' spirit trapped in a doll who becomes upset when he is away from Anju too long. In volume 3 of the manga one of Anju's classmates takes Boogie-kun, with grievous consequences until Anju comes to take Boogie-kun back.

In the anime, Boogie-kun reverts to being an inanimate doll after Anju awakens as a full vampire in episode 20.
(Source: Wikipedia)