Sayaka Iijima, a student at Shirakumo Academy, approaches her chemistry teacher Sakurai Shino seeking guidance over personal anxieties regarding sexual matters. She expresses distress stemming from pressure by her boyfriend, Tamotsu Abe, to engage in sexual activity. Prompted by Sayaka's concerns, Shino initiates an unconventional sex education lesson involving both Sayaka and Tamotsu. This lesson includes explicit demonstrations, during which Shino demonstrates fellatio on Tamotsu. Witnessing this interaction triggers a possessive reaction in Sayaka. She intervenes physically, pushing Shino away from Tamotsu and declaring her claim over him, signifying a shift from initial hesitation to assertiveness regarding her relationship. Though unorthodox, the lesson resolves the immediate tension in Sayaka's relationship with Tamotsu. She moves from worry and confusion to actively defending her relationship during Shino's demonstration.