Chiaki Shinomiya reunites by chance with her former high school homeroom teacher, Kazama, and invites him to her home. She learns that his wife passed away a year ago, leaving him in a state of apathy, causing him to quit his teaching job and remain unemployed ever since. Back in high school, Kazama had always supported her—guiding her through academic, career, and personal issues—and she once dreamed of becoming a teacher just like him. Wanting to help lift his spirits, Chiaki decides to pleasure him orally in an attempt to bring him comfort. However, Chiaki herself is struggling: she has been coerced into a sexual relationship by her student, Hiro, and ultimately gave in. As a result, she has become Hiro's sex slave. As she confesses this painful truth to Kazama, their emotional bond gradually deepens.