When ace high school detective Jimmy Kudo is fed a mysterious substance by a pair of nefarious men in black - poof! He is physically transformed into a first grader. Until Jimmy can find a cure for his miniature malady, he takes on the pseudonym Conan Edogawa and continues to solve all the cases that come his way.

At a mystery-themed college party, a fire threatens the life of a pretty freshman - and Conan suspects arson. But Rachel is more worried by the discovery that the victim has a past with Jimmy Kudo. Can she compete with Jimmy's beautiful, brilliant first love? Then the Junior Detective League stumbles upon a counterfeiting operation led by a woman in black, and Conan finds himself on the trail of the shadowy crime syndicate that turned him into a kid - not to mention the scientist who created the de-aging formula!