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.
Unfortunately the movie Butt Detective the Movie: Shiriarty is not yet available on HBO Max.
| Directing | Yuriko Kado | Director |
| Visual Effects | Hideaki Maniwa | Character Designer |
| Sound | Ryuta Nakahara | Sound Effects |
| Art | Ryutaro Masuda | Art Designer |
| Visual Effects | Kumiko Yanagisawa | Color Designer |
| Production | Masahiro Murakami | Production Manager |
| Sound | Hiroshi Takaki | Original Music Composer |
| Production | Katsuhiro Takagi | Executive Producer |
| Production | Hitoshi Chiba | Executive Producer |
| Production | Hidenobu Muramatsu | Executive Producer |
| Production | Yuji Shibata | Executive Producer |
| Production | Naoshi Yoda | Executive Producer |
| Production | Koko Tanigami | Producer |
| Writing | Katsuhiko Chiba | Screenplay |
| Visual Effects | Alejandro John Belen | Animation Director |
| Visual Effects | Dennis Cablao | Animation Director |
| Visual Effects | Dennis Cablao | Key Animation |
| Art | Yuriko Kado | Storyboard Artist |
| Art | Kazuhiro Ochi | Storyboard Artist |
