The singers of TWO-MIX were kidnapped by two men. Conan and the Detective Boys were with one of the members and tells Inspector Megure what happened. The kidnappers want a tape that TWO-MIX sang because it had hints that led them to a crime they had done a while ago. The kidnappers want the Detective Boys to deliver it but then later, the kidnappers want Ayumi alone to deliver the tape. In the end, the Detective Boys manage to rescue TWO-MIX just in time for their concert.

Kudo Shinichi is a seventeen year-old high school detective whom people call the "Modern Sherlock Holmes." However, one night after a date with his childhood sweetheart, Ran, Shinichi witnessed an illegal trade and, caught off his guard, was knocked unconscious and fed a drug that was supposed to kill him... but he woke up and found himself shrunken to a seven year-old. In order to track down the men who did this to him, Shinichi hid his identity and lived with Ran, whose father happened to be a hopeless detective, and with that came a series of murders and mysteries that he must solve.