The Detective Boys visit a pet shop and find the owner, Minoru Shirai, dead. They find a Rhinoceros beetle and pamphlets of an insect museum at Gunma Prefecture. Takagi drives the Detective Boys to the museum where they learn that a truck load of Rhinoceros beetles were stolen from the van. Conan investigates and realizes Shirai and an accomplice were the thieves and that the accomplice was the murderer. Deducing from his investigation that the accomplice is one of the employees at the museum, Conan tranquilizes Yamamura and reveals Takashi Ishida to be the culprit. Conan explains that evidence on Shirai's body suggested he was murdered in the van and was strangled by a strap from the museum. As further evidence, Conan reveals that he saw a message from Ishida's phone that proves he was selling the stolen Rhinoceros beetles. Ishida confesses to the murder and explains that Shirai was always insulting him.