Two mother-son pairs live next door to each other in an apartment building and are good friends. However, the sons have a vague suspicion that their mothers are too close to each other. Then, one day, they accidentally witness a shocking scene. The mothers are being penetrated by the burly liquor store guy who always comes by. And what is the plan that the two sons have come up with? Enjoy the unexpected, fast-paced drama and incestuous swapping.