Hikawa Jun lost his mother at birth and grew up without any memory of her. He watches his classmates complain about their overprotective mothers and wonders what it would feel like to have one of his own. Craving maternal warmth, the middle school boy lies about his age and signs up for a sugar mama dating app. There he matches with a woman named Hasuda Saki, who agrees to act as his mother for a time. Their arrangement eventually comes to an end, and they part ways.

Years later, when Jun is in high school, Saki re-enters his life under completely different circumstances: she has married his father and becomes his stepmother. Now living under the same roof, Saki insists on fulfilling the role of a real mother, but her idea of motherhood begins to blur the line between parental care and something more unsettling. She offers to teach Jun about women’s bodies so he will be ready for future relationships, an act that stirs confusion and a new kind of awareness in him. As he becomes conscious of feelings that go beyond filial affection, Jun must navigate a deeply tangled relationship with the woman who was once a stranger he paid to be his mom and is now his legal guardian. The story follows the distorted bond formed between two people starved for love, bound not by blood but by a fragile, shifting arrangement.