Mousou Dairinin is about a social phenomenon in Musashino, Tokyo caused by a juvenile serial assailant named Lil' Slugger (Shounen Bat, or Bat Boy in the original Japanese version). The plot relays between a large cast of people affected in some way by the phenomenon; usually Shounen Bat's victims or the detectives assigned to apprehend him. As each character becomes the focus of the story, details are revealed about their secret lives and the truth about Shounen Bat.

[Source: Wikipedia]