Hana and Tsugumi are cousins. Both have been dating their boyfriends since student days and have promised to marry them. One day, they went on a hot spring trip with their boyfriends to celebrate their engagement. However, the inn they headed to was in financial distress, and the owner had fled, leaving yakuza occupying the property to prevent it from being auctioned off. Unaware of this, the two couples arrived and were forced into a hellish situation where they had to swap partners and engage in unprotected sex swapping…
