Haruka, a gentle and naive high school student, looked forward to the arrival of her newly acquired step-brother, Tsukasa. Prior to this, she had been living independently because of her father's job abroad. However, with the remarriage of their parents, Tsukasa would be residing with her while their folks are away. Upon meeting him, Haruka found Tsukasa to be more endearing than she had anticipated. He sought her aid in his studies and asked to share her bed. But as he expressed his desire to undress and have sex with her, Haruka felt taken aback and disturbed.
