is a Japanese anime television series created by director Satoshi Kon and produced by Madhouse about a social phenomenon in Musashino, Tokyo caused by a juvenile serial assailant named Lil' Slugger (the English equivalent to Shonen Batto, which translates to "Bat Boy"). The plot relays between a large cast of people affected in some way by the phenomenon; usually Lil' Slugger'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 Lil' Slugger.