The otaku is a character first introduced in episode 2 on the news when he is talking about Shonen Bat. He is later seen as one of Maria's clients in episode 3.
He has several dolls including Vilda (the only referred to by name) and the bunny, cat and witch.
In episode 12 his home is visited by Maniwa. His dolls refer to HIM as a doll.
The dolls show Maniwa that the figurines which the otaku is sculpting are the victims of Shonen Bat.