Mariko Kayane, 18, attends design school and has a boyfriend: Nishimura Shōichi a boy who became popular playing football, so much so that girls stop him on the street to ask for his autograph!
During a date with Shōichi, Mariko finds a very nice book, illustrated by a certain "Tsunokiyoshi" who turns out to be a 34-year-old teacher. Although he is almost twice his age, Mariko begins to take an interest ...