Saki, who harbors deep feelings for her older brother, keeps her pure emotions hidden in her heart. Her brother, unaware at first, gradually becomes conscious of her affection and begins to truly cherish her in return. To strengthen their bond, they embark on a private hot spring trip together. However, during their journey, Saki falls victim to a corrupt masseuse who toys with her body, leaving her aching with desire. Unconsciously thinking of her brother, she secretly begins to masturbate. At that very moment, her brother—having finally acknowledged his own feelings—appears before her, determined to protect her and confess his love.