Best friends Hikari and Rei are both troubled by poor sexual compatibility with their husbands. After talking it over, the two couples separately visit a swingers bar hosting a masked-party event. Swept up in the provocative atmosphere, Hikari's desire to dominate and Rei's desire to be dominated burst free behind their masks. Only afterward do they discover that each woman has been having sex with her best friend's husband, drawing both couples toward pleasure-fueled wife swapping and 4P sex.