Mamoru Kagemori is a dull high school boy who's not handsome, athletic or intelligent - but he is actually the eldest son of the 400-year-old Ninja clan specialising in protecting their neighbours, the Konnyakus! One day a transfer student confesses her love to Mamoru... What will he do? Meanwhile Yuna is made into an alien, and other crazy characters appear as hysterical news of a UFO spreads.