Osananajimi to Doukyuusei  

소꿉친구와 동급생, 幼なじみと同級生, Osananajimi to Dokyusei

Miyu was on her way home from school when a train molester groped her breasts. Shun, her classmate, intervened and saved her. He then walked her home and teased her about the chikan incident. Later that night, Miyu regretted losing her first kiss to Shun. When she got home, Kou, her childhood friend, took her to his house because she lost her key. There, Miyu confessed that her first kiss was stolen. However, Kou told her they had already kissed, so it wasn't her first kiss. That night, Kou took Miyu's virginity. The next day at school, Shun apologized and invited her to his house. Miyu accepted not knowing it was a trap. There, Shun drugged her and trained her as a sex slave. She resisted at first but eventually started masturbating. It is unclear if Miyu actually enjoyed the experience or wanted more. Similarly, Kou's actions are also ambiguous, as he took her virginity without her consent.