Since Rei Aoki moved in as his father's new wife, Makoto has grown suspicious of her true intentions. Though she was welcomed into the family as an older stepmother figure, her behavior and attitude make him deeply uneasy, wondering if she's only after money. One night, Makoto secretly peeks into Rei's bedroom and catches her masturbating alone. Shocked by the sight, he begins to corner her whenever his father is away. Using humiliation as a weapon, he forces her into embarrassing positions, gradually transforming her into a lewd, lustful woman. Along the way, Makoto's own feelings start to waver.