A pickup artist has repeatedly asked his girlfriend (sex friend) to star in an adult video, but has been turned down. One day, she introduces him to her younger sister, who just turned 18. She's so cute that he tries to woo her without his girlfriend knowing, and they end up having sex. After that, he films himself having sex at her house every day, so that she doesn't find out. When he asks her to star in an adult video after she's gotten used to being filmed, she says, "I'll keep it a secret from you, sister," and so he ends up having a threesome in an adult video.