Takefumi Kooriyama's death was an 'accident. The death characters were coincidental flukes made by candies and a thumb edge in Kooriyama's case, and coins, the edge of a wallet, and a cigarette in Isao's case. Megure correctly ruled Isao's case to be a theft as some thieves stole Isao's wallet post-mortem. The thieves returned to the crime scene and attacked Sera, Ran, Sonoko, and Conan to cover their involvement in the theft. A little Jeet Kun Do, karate, and a well placed soccer ball dispatched the thieves easily. Sera's thoughts at the end of the episode seem to indicate she knows something about Shinichi's past.