32-year-old Minako is a Japanese language teacher at a high school and also the advisor of the koto club. One day, a new transfer student, third-year student Yume, joins the koto club, and Minako falls for her at first sight. Overcoming the barriers between teacher and student, Minako uses her position as club advisor to invite Yume to a koto recital. However, Yume declines, saying her parents are away on a trip and she'll be lonely at home. That night, Minako ends up spending the night at Yume's house, leaving them completely alone together. A forbidden relationship begins to bloom between the teacher and her student, each intense moment drawing hearts ever closer.