Attending the same university and belonging to the same club, Yuna & Masashi couple and Ai & Kida couple often go on dates together, and all four are close friends. With their respective anniversaries approaching, the four of them came on a trip. Knowing it was wrong, Yuna and Kida still had a one-night-two-day sex marathon behind their partners' backs. 'I love my boyfriend, but the sexual compatibility with my best friend's boyfriend was the best...'
