Mother Chisato can't hold it in and relieves herself in the yard, accidentally witnessed by her son Ryota passing by. The sight triggers intense sexual arousal in Ryota, who then uses a diuretic to make his mother wet herself again, giving in to his urges and assaulting her. He overcomes Chisato's resistance with an aphrodisiac, gradually drawing her into a twisted bond where they begin to form a disturbing emotional connection. The story unfolds with shocking developments and deep transformations in their complex relationship.