Yui, an enthusiastic mother, discovers a hidden folder on her son's computer, which contains a large number of erotic anime images. Suspecting that he has no interest in real women, Yui tries to use her own body to find out his sexual preferences. She goes into the bathroom where her son is and, while washing, shows him her naked body and private parts. Her son pretends not to notice, but gets an erection. Ignoring this, Yui continues to provoke him. Gradually, an eerie atmosphere begins to take over the room...