Ichirou Satou, a second-year high school student, has always been an ordinary person—that is, until he encounters some not-so-average scenarios with his teacher, Kana "The Demon" Kojima. Satou's Japanese language instructor, Kojima, has a reputation for being so merciless that even school delinquents submit to her. When Satou runs into Kojima in the lavatory one fateful day, they enjoy an intimate encounter that leaves his imagination running wild for days. Sensei, Nande Koko ni ga? follows Satou and his teacher's daily lives as they continue to meet under similar circumstances, becoming closer with each meeting.