Kagemori Mamoru is an unassuming boy with messy hair and thick glasses, yet he is actually the son of a ninja family. For 400 years, his family has secretly protected their neighbors, the Konnyaku clan. Mamoru has personally guarded their daughter, Konnyaku Yuuna, since kindergarten. Whenever Yuuna gets into trouble, Mamoru dons a ninja outfit and transforms into a capable ninja to assist her.