Youngsook is trying to get her nipples to move, but it's too soft, and her dick can't get enough of it. He's worried that she's just thinking about the "old days" when they were younger, when they used to bathe by the river together. He tells her to wipe his back, but she won't do it, because he's acting like a "little brother" to her. He worries that if she touches his ass, he'll have sex right away, and he wants to wash it properly.