A happy couple (with big-breasted wives) who are on vacation are approached at a hot spring resort and enter the men's bath together to take on a cuckold mission with a cash prize! If they can have sex with a male guest and cum inside, they can win a prize of 1 million yen! With the power of money, the cum shot that was thought to be impossible gradually becomes a reality... Will the big-breasted wife's first affair take place right in front of her husband?! A carefully selected collection of 4 couples!