The saying "the grass is greener on the other side" actually reveals an unexpectedly intriguing side when examined more deeply. Realizing that their friends' mothers have a surprisingly kind and erotic side, mischievous friends begin swapping mothers one after another for pleasure. Of course, they willingly offer their own mothers to their friends and take pleasure in watching them. This taboo act of quasi-incestuous swapping has become an increasingly popular indulgence.