Juzo Ogami has never led a normal life. He was picked up by a criminal organization as a child and grew up to become a legendary hit man. But everything changes when he's bitten by a mysterious insect and becomes a teenager again! Can this battle-hardened assassin handle the rigors of middle school life?!

Mitsuoka Pharmaceuticals is responsible for Juzo Ogami's sudden transformation into a middle schooler, and now Juzo is in a fake relationship with none other than Noren Mitsuoka, the heir to the company! But that means having to protect his position from the numerous men who seek Noren's hand in marriage. The challengers include fellow hit man Shin and superathlete Tenma Tendo. Can Juzo defeat all of them?!