Professor Agasa takes the Detective Boys with him to an onsen (warm spring) to fix a product the propietor purchased from him. At the onsen, the kids are introduced to four cast members filming a drama about a hitman. Since the bath is crowded, the kids decide to bathe in the early morning. As they head to the bath, Ai and Ayumi discover the Ganji Tetsuyama, the scriptwriter, inside the bath's women section, dead.
Elenco: Minami Takayama , Kappei Yamaguchi , Wakana Yamazaki , Akira Kamiya , Rikiya Koyama , Megumi Hayashibara , Kenichi Ogata , Ikue Otani , Wataru Takagi , Chafurin , Yukiko Iwai , Kotono Mitsuishi , Kikuko Inoue , Fumihiko Tachiki , Hideyuki Tanaka , Kenichi Ogata , Sumi Shimamoto , Unsho Ishizuka , Yukiko Iwai , Yukitoshi Hori , Yuko Miyamura , Wakana Yamazaki , Kappei Yamaguchi , Minami Takayama , Akira Kamiya , Rikiya Koyama , Ryotaro Okiayu , Ai Orikasa , Atsuko Yuya , Hiroyuki Kinoshita , Asako Dodo .