J is a professional hitman, orphaned and raised by a syndicate to kill. He proved too skilled and learned too much, so the syndicate tried to get rid of him, and the attempt went badly for them. After three syndicates were destroyed, he became known as untouchable. Megumi is a third grader whose classmates bully her for being half-Japanese, half-American and for her good grades. When the two knock heads, their bodies switch: the hardened killer ends up as a cute schoolgirl, and Megumi finds herself in his tough frame. Now they must keep the change secret and make their daily lives look the same as before. J gets a hard lesson in how difficult a girl's life can be, while Megumi seems to enjoy her new one. The result is a body-swap action comedy.