A cold marital relationship. Wife Aika feels increasingly lonely as intimacy with her husband fades away. She begins noticing changes in her body—her skin growing more sensual, her figure becoming fuller—and starts secretly wearing corrective lingerie she purchased. One day, her much younger brother-in-law catches sight of her in her undergarments. Overcome with arousal at his sister-in-law's seductive appearance, he gives in to temptation, leading them into a forbidden relationship. Despite knowing their love is wrong, both are drawn deeper into an illicit affair.