A young woman approaches the Boy Detectives' Club and asks them to find the intended recipient of a series of threat letters her boyfriend made. They accept the job and begin to tail her boyfriend. Meanwhile Kobayashi, after missing his chance to return Hanasaki's dropped wallet, uses it to buy a desperately needed meal. Hanasaki finds out by checking his electronic money usage history, and he convinces Kobayashi to join him on the current investigation in a second attempt to get him to join the club...
With all the customers he gets, 
he'll forget me in a heartbeat.
Bei all den Kunden hat der mich bald vergessen.
Con todos los clientes que tiene,
se olvidará de mi en un segundo.
Com os clientes que recebe,
ele me esquece rápido.