Husband harbors a secret "cuckold" fantasy he can't tell his wife, so he applied to SOD. Three young couples with the same desire are invited on an onsen trip. While the husbands briefly leave the mixed bath, nearby couples suddenly start making out—exposing fully erect dicks! At the souvenir shop, the wives get excited trying out vibrators. Ultimately, despite their husbands being right beside them, the wives—overstimulated from massage—shockingly accept strange men's dicks!