She has a boyfriend. They have sex to a certain extent. But it's become a rut and she's not excited. Of course, her older sister, who lives with her, also has a boyfriend, and she is very satisfied with her fulfilling sex life with him. When the younger sister secretly sees her like this, she has a dark desire in her heart to have sex with her older sister's boyfriend! At first, it's just a light mischief. But when she seriously seduces her older sister's boyfriend and has sex with him, she becomes addicted to the sense of immorality! The younger sister is addicted to a dick that is different in size and duration from her boyfriend's! She loves her older sister and has a good relationship with her sister, but she can't stand this! A kind older sister who cares for her younger sister, and a wicked perverted younger sister who works behind the scenes. And the older sister's boyfriend, who is at the mercy of this, is caught in the quagmire of NTR from which he cannot escape! A complete collection of the most thrilling and erotic cuckolding that will make you feel nervous and excited just watching!