Case Closed - Season 1 - Eps 655: The Design of Poison and Illusion (Illusion)
Conan and Heiji's investigation leads them to realize how Ikuro and Serika were murdered. They reveal that when two pieces of the baumkuchen were left, they were rearranged using the Jastrow illusion and applied poison to the seemingly larger piece. For Serika's murder, the same culprit used the Gestaltzerfall phenomenon while she was signing contracts. This caused her to forget how to write the Waka (若) kanji forcing her to open a dictionary to the Wa (わ) pages where poison was applied. They reveal the culprit to be Satake, evidenced by the shine on her bronze watch due to a chemical reaction with cyanide. Satake confesses to the murders and explains it was to avenge Wakamatsu who was secretly her father. In the aftermath, Kazuha attempts to confess her feelings to Heiji but fails when he leaves partway.
About Case Closed

Title: Case Closed
First Air Date: 1996-01-08
Last Air Date: 2025-03-08
Status: Returning Series
Rating: 8/10 (from 683 votes)
Language: JA
Seasons: 2
Total Episodes: 1157
Network: YTV
Genres: Animation, Crime, Mystery, Comedy
Production Companies: TMS Entertainment, Kyokuichi-Tokyo Movie
Synopsis
The son of a world famous mystery writer, Jimmy Kudo, has achieved his own notoriety by assisting the local police as a student detective. He has always been able to solve the most difficult of criminal cases using his wits and power of reason.
Cast

Minami Takayama
Conan Edogawa (voice)

Kappei Yamaguchi
Shinichi Kudo (voice)

Wakana Yamazaki
Ran Mouri (voice)

Akira Kamiya
Kogoro Mouri (voice)

Rikiya Koyama
Kogoro Mouri (voice)

Megumi Hayashibara
Ai Haibara (voice)

Kenichi Ogata
Hiroshi Agasa (voice)

Yukiko Iwai
Ayumi Yoshida (voice)

Wataru Takagi
Genta Kojima (voice)

Ikue Otani
Mitsuhiko Tsuburaya (voice)