On a night when their parents are away, Mari and her brother secretly indulge in their forbidden relationship. Pretending to be nothing more than quarrelsome siblings, they steal kisses whenever they can and sneak off to hidden places to have sex. To confirm their feelings, the two make love over and over again in the privacy of their room. At one point, the brother whispers to Mari, "Finally, we're all alone. Let's have sex as many times as we want, wherever we want, all day long. And when I come, I'm shooting everything deep inside you, okay? Just for you, Mari."