The senior I've had a crush on for ages has a new girlfriend with big tits... Because she has little experience with women, I hide my feelings for her and practice sex with her using my breasts in secret - Reina Momozono - Reina Taozono

The movie revolves around Reina, who has had a long-standing crush on her senior, Jun Yoshino. However, he already has a girlfriend named Anna. Despite this, Reina offers to help Jun practice intimate activities using her own body, allowing him to gain experience and confidence. As they engage in these secret practices, Reina's feelings for Jun persist, while Jun struggles with his own desires and sense of loyalty to Anna. The story explores the complex relationships and tensions between the characters, delving into themes of unrequited love, secrecy, and intimacy.