High School Female Teacher: Defiled Sex(2001)

One day, Sayoko is raped by a masked man after school, but afterwards, she asks her student Takao, who enters the classroom, to keep it a secret. A few days later, Sayoko finds an envelope containing a threatening letter. Sayoko confides in Takao and goes with him to the meeting place, but no one shows up. Terrified, Sayoko calls her husband, Koichi, but it's his mistress, Yuki, who answers the phone. Takao gently comforts the wounded Sayoko, and they finally sleep together...