The man who came to Mouri Detective Office, Masao Kouda, claimes that his sister was murdered and buried in Yoshikazu Watanuki's yard. When the Detective Boys hear of this story, they're surprised. They just met Watanuki when their softball landed on his yard. But Kokogo replies that he can't help because of a lack of evidence....that mean is time for the Detective Boys!! But that weekend, Kouda is stealing jewelery. It turns out that his job offer was just a camoflauge. There is only one truth!