Best friends Hikari and Rei are both troubled by poor sexual compatibility with their husbands. After discussing the problem, the two couples separately visit a swingers bar during a masked-party event. The charged atmosphere unleashes Hikari's urge to dominate and Rei's craving to be dominated. Behind their masks, neither realizes that her partner is actually her best friend's husband, setting both couples on the path to pleasure-driven wife swapping and 4P sex.