At the beginning of the story, 17-year old (16 years in the manga) high school student Jimmy Kudo (Shin'ichi Kudo) becomes the boy, Conan Edogawa. Jimmy Kudo in the beginning of Case Closed is known as a high school student detective. One day, Jimmy goes to a theme park named "Tropical Land," with his childhood friend (or current girlfriend), Rachel Moore (Ran Mori). He encountered a case where a roller coaster passenger, Kishida (Kenneth in the English anime), is killed in a spectacularly bloody decapitation
He solved the case and on his return home, he witnesses a suspicious deal involving some men dressed completely in black. Another man in black spots him, knocks him down, and gives him an untested poison named Apotoxin-4869 (APTX4869), which is intended to kill him. The poison does not kill him. However, when he comes to his senses, his body has shrunk down to the size of an elementary school boy.
