Shinichi Kudo is a brilliant high school detective often called the "Sherlock Holmes of the Modern Era." During an investigation into two suspicious men in black, he is ambushed and forced to ingest an experimental poison. Instead of killing him, the drug deforms his body into that of a seven-year-old boy.

Adopting the pseudonym Conan Edogawa (inspired by Arthur Conan Doyle and Edogawa Ranpo), he moves in with his childhood friend Ran Mori and her private investigator father, Kogoro. By using gadgets invented by his neighbor Dr. Agasa, Conan secretly solves Kogoro’s cases for him, building the older man's reputation while desperately searching for clues to the mysterious Black Organization and a way to regain his original body.