Episode 849: The Marriage Registration's Password (Part 1)
Scenario: When police Officer Yumi Miyamoto sees a news story about the shogi championship match, she learns for the first time that Haneda is a professional shogi player. Several years earlier, Yumi received an envelope from Haneda and was instructed not to open it until he had acquired "all seven." Haneda has now won all seven major shogi titles. Detective Sato reasons that the envelope's contents must be a marriage registration, but Yumi threw out the magazine she kept the envelope in that morning. They immediately head to the dump site, but the magazine is gone. Conan and the Detective Boys attempt to help Yumi find the envelope.
Yumi was unaware of Shukichi being a famous shogi player for a long time, mostly due to her lack of interest in investigating, and an apparent personal disinterest in shogi (she is more of a Mahjong type). She assumed Shukichi was a "meijin" at some minor game like shiratori or fishing. She eventually saw Shukichi on television and figured it out. After realizing that meijins can make 100,000,000 yen in salary, she desperately tries to reclaim an envelope he left for her, which her ornery building manager had seized. (After Yumi had mistakenly put it in an old magazine and took it out to the trash on the wrong day).
The envelope was given to her by Shukichi Haneda, and was said to open it when he had collected all seven. Those seven were figured out to be the seven titles of shogi meijin.
The building manager, a shogi fan and a former pickpocket, looked inside the envelope to find the marriage registration form, and made a game that would uncover the 8 digit password for the marriage registration. The game was for the purpose to challenge Yumi, whom he called 'ChaCha', and to find if she was worthy of being Shukichi's wife.