Some city in northern Kanto. The beautiful mother-in-law, Misao, lives with her husband and son. One day, after shopping, she lost the key to her house and was at a loss. Since she had been holding back her urine all this time until she got home, she hurriedly searched for the key at the side entrance but didn't make it in time and ended up "urinating herself" there. A son accidentally witnesses his stepmother's embarrassing bedwetting upon returning home from school… From that day on, the stepmother falls into an unspeakable tragedy of forbidden bedwetting training and incest…
