With her husband away on a solo work assignment and rarely returning home, the mother is left feeling lonely. Her two sons, concerned for her well-being, grow closer to her in different ways. The younger son, Koji, accidentally discovers his mother masturbating and, using this secret, gently draws closer to Kanami, sparking an intimate relationship between them. Meanwhile, the older brother, Shintaro, uncovers their affair. Shocked by her sons' reactions, the mother is pushed toward an inevitable conclusion. A complex tale of human relationships unfolds, entwining emotions, familial bonds, and forbidden desires.