In the Kawauchi household, a single mother and her son's quiet life is disrupted one night by a sudden power outage. As they leave the son's study room to investigate, the only source of light—the flashlight—accidentally shines up the mother's skirt while she stands on a step ladder in the dark. Under the unusual glow, the son can't help but notice the sensual curve of her thighs, stirring unexpected feelings. After that night, blackouts occur more and more frequently, throwing their daily routine into chaos and leading to a series of intimate, forbidden encounters.