Masaru, the son, accidentally witnessed his mother, Mari Yamaguchi, masturbating one night six months ago. Since then, he has secretly watched her every night from the shadows. Having seen her act repeatedly, he began developing intense sexual feelings toward his mother that he'd never experienced before. Meanwhile, the mother, growing increasingly lustful with age, found herself unable to suppress her desires and continued masturbating frequently. One day, the son began pleasuring himself while whispering his mother's name. At that moment, his heart pounded harder than ever, his breath turning ragged with arousal.