The Shidoshi, a long-absent ninja clan bent on absorbing or destroying all inferior ninja, has been setting its sights on Quagmire, U.S.A., mostly due to the small population of ninja living there. Their leader, Yuudai, is determined to defeat teen ninja supreme Ricky Feeple, so he signs up to attend Ricky's high school! While Ricky weathers daily battles, his classmate Pete yearns only to be the best dishwasher in the world. If only he didn't have that annoying talent for tennis. Ricky's troubled teammate, the ex-assassin Suzume, discovers a new friend in Dawn, a classmate who happens to be a Grim Reaper! His would-be rival, Tetsuo, has gone on a quest to conquer a mountain and find his true path in life. His fun-loving thief friend Sora gets a visit from her dear Granpa Rumpy, and she asks Ricky to help her steal some rare tea for the occasion. But "Granpa" wants more from Sora than just tea...