A female student, Narumi, is being taught by her private tutor, Matsumoto, and is also dating him. Being considerate of Narumi, who is still a student, Matsumoto only performs oral sex on her. Despite Narumi's innocent heart, she has impressive fellatio techniques. One day, Matsumoto is threatened by Nakata, a senior from her hometown. Matsumoto owes money to Nakata and is being pressured to repay it. Matsumoto is then forced to offer Narumi as collateral for the debt...