Episodes 518-519: Meiji Restoration Puzzle Journey (Exploration & Deciphering) ★★★

Kogoro Mouri is asked by Kouko Kohayakawa to investigate her grandfather's diary because someone has been trying to steal it. Conan discovers a treasure hunt cipher hidden within the diary, and heads to Tsuwano, Shimane Prefecture with everyone else to solve the mystery. During the treasure hunt, Kouko, Mitsuhiko, and Haibara are kidnapped by a masked man. Conan must decipher the cipher under duress, find the treasure, and uncover the group's true intentions. The final treasure isn't the gold and jewels one might imagine, but rather a letter related to the Kohayakawa family's aspirations, along with a valuable misprinted stamp attached to the envelope. This twist elevates the meaning of the treasure hunt beyond mere monetary value, highlighting that what a grandfather leaves behind can possess value on multiple levels. *The episode numbers I've listed are for the Japanese broadcast; they are not the overseas versions. Overseas broadcasts sometimes split longer episodes that weren't originally divided into parts, resulting in more episodes. For instance, these two episodes are 518-519 in Japan and 567-568 overseas.