Kabamaru is a young boy raised and trained by his grandfather as a ninja. After the sudden death of his grandfather, he starts living with Mai, his grandfather's mistress, who is a school director. He is asked to help out on struggles against other schools, as he is master of the ninja mystical arts. As time passes he will make lots of friends as well as enemies, and fall in love with Mai.

television series

昭和23年4月、志麻洪介は愛媛の松山高校に入学し、寮生活を始めた。同室者はホルタン、オンケル、アルル、丘頭の4人。間もなく洪介は県立高女のマドンナ・房子に恋をした。夏休みが終わり、秋の文化祭の準備が始まった。洪介たちは芝居「理髪師チッターライン」をやることになったが、肝心な恋人役のアガーテがおらず房子に白羽の矢が立った。演出はオンケル、レオンハルト役は洪介が務めた。練習中は恋のさやあてなどもあったが、房子を囲んだ楽しいものだった。文化祭は成功のうちに終わったが、オンケルも房子に惚れ込み、洪介を通して気持ちを打ち明けたが、受け入れられなかった。オンケルは失意のうちに寮を去った。昭和24年の春、洪介は九州大学に入学。博多で元気そうに演劇人を志すオンケルと再会。洪介は松山に戻り、房子に別れの言葉と共に愛を告白するが、彼女は「長い間その言葉を待っていた」と答えた。しかし、二人は結ばれずそれぞれの人生を歩んだ。...

同名动画的电影真人版。
“The plot centers around a five part competition between Kabamaru representing Kin'gyoku School, and Hayate representing Ōgyoku School. The five events are falling from a height on a balloon (Kabamaru wins), swimming (Hayate wins), throwing shuriken while horseriding (Kabamaru wins), food eating contest (Hayate wins - Kabamaru is disqualified because he missed an olive) and remaining on the roof of a car driven by a student of the opponent school (Kabamaru wins after being promised 1,000 plates of yakisoba noodles by Shijune).”