Conan and Heiji investigate how only one piece of an evenly cut cake was poisoned. They discover a biodegradable capsule in a tea cup, suggesting the poison was delivered through a clever concealment method.
Powdered poison is discovered on Ikuro's doorknob and Serika's slippers, initially framing her for the crime. Detective Conan Episode 653
This arc is notable for the early appearances of Masumi Sera , who continues to observe Conan’s detective skills. The Design of Poison and Mirage - Detective Conan Wiki Conan and Heiji investigate how only one piece
Ikuro Wakamatsu, age 25, who dies from cyanide poisoning after eating a piece of baumkuchen (cake). Detective Conan Episode 653