Paranoia Agent (2004)

Musashino, Tokyo. An elementary schooler repeatedly attacks people in the streets. Known only to the public as "Lil Slugger", none of the victims can recall the young boy's face and only three distinct details are left in their memories: golden inline skates, a baseball cap, and the weapon: a bent golden baseball bat. Detectives Ikari and Maniwa set out to track down the perpetrator and put an end to his crimes.