The protagonist gets a new sister after his father's remarriage. Mio, the eldest, and Monami, the second daughter, are stunning big-titted beauties with incredible figures, and just living under the same roof is enough to make his heart race. However, since the sisters' rooms aren't ready yet, he's forced to sleep in the same room with them. With no way to fall asleep, he becomes acutely aware of their bodies lying beside him. Their exposed nipples and bare thighs draw his gaze, and being sandwiched between them feels like an agonizing, irresistible torture. Overwhelmed by the sensation, he writhes in pleasure, completely entranced until morning. The tension is palpable, as the relationship with his new sisters teeters on the edge of something about to begin.