They're twins, so they look alike, but their personalities are polar opposites! The older sister is active, good at studying and sports, and popular with guys, a typical top-tier girl. On the other hand, the younger sister is plain and shy around guys, a typical gloomy girl who can't compete with her older sister at all! But there's one thing she can beat...! And that's sex! The plain younger sister forcefully seduces her older sister's boyfriend! The older sister's boyfriend can't resist the younger sister's techniques, who is actually a sex genius! Although she's usually quiet, when it comes to sex she moans like a different person and attacks aggressively!