Say no and moratorium

When Mitsu was in high school, he had a physical relationship with his childhood friend Nana, whom he had a crush on. However, when Nana suddenly asked him, "Do you want to stop doing this kind of thing?" Mitsu was unable to tell him that he didn't like it, and ended up heartbroken. Mitsu has not been in contact with Nana since then, but his feeling for him still remained.
When Mitsu became a university student, he runs into him again while working part-time. He is relieved to find that he doesn't seem to notice him, but short after, he is ambushed at the end of his shift and they end up going to Mitsu's house together. There, Nana shows his obsession with Mitsu for some reason. While the memory of his hurt returns to him, Mitsu's feelings for him still remain…