A baffling series of crimes turns out to be the work of Shiriarty, a villain who seeks to steal a mysterious treasure known as the "O-PARTS". Oshiri Tantei along with his assistant, Brown, enlist the aid of Audrey, an investigator from the international police organization Wanterpol, in an effort to prevent the "O-PARTS" from falling into the wrong hands while Shiriarty strives to plunge the world into darkness.
| Actor | Role |
|---|---|
 Yuko SanpeiButt Detective (voice) | Butt Detective (voice) |
 Mie SonozakiAudrey (voice) | Audrey (voice) |
 Ayaka SaitoBrown (voice) | Brown (voice) |
 Masaharu FukuyamaShiriarty (voice) | Shiriarty (voice) |