Waka returns to her room after exercising, sweating and wanting to stretch. To her surprise, her younger brother Riku is there, cooling off in the air-conditioned room. Annoyed but eager to stretch before her body cools down, Waka begins her routine. Sweat drips from her cleavage, her big ass jutting out as she moves. Though aware of their sibling relationship, Riku can't help but stare. Noticing his gaze, Waka presses her big tits against his back under the pretense of teaching him stretching. "Hey, you've been looking at your sister this whole time, haven't you? I know what you're doing." "W-what? Is that bad?" "We're siblings, after all... But if you're curious, why don't you touch them?" Hesitantly, Riku starts groping her breasts. Overcome by desire, he gives in completely, ultimately breaking the taboo and having sex with his sister, filling her with a creampie.