Otoko Gakuin Soushi Shinobi no Otoko

Shigeru Hazuki is a 26-year-old ninja with outstanding combat ability. To protect young Master Shinobu, he infiltrates a high school while posing as a student. There he gets drawn into the duties of the Disciplinary Committee's new president, Asato Kusumi, and encounters Mitsugu Kisaragi, a former bully now hiding as a math teacher.