Late one night, the phone suddenly rings. "I missed the last train—can I come over now?" It's a request from her younger sister, Miyu. Though you initially want to refuse, her persistent charm pulls you in, and you end up letting her stay. She arrives, takes a bath, then relaxes on the sofa in her nightwear. From the edge of her lounging outfit, a soft, generous cleavage peeks out, gradually stirring your emotions. When she teasingly asks, "You're looking at my breasts, aren't you?" you stammer, "Huh? Were you showing them on purpose?" Her coquettish, mischievous aura makes it feel like she's deliberately seducing you. As she playfully moves her lips closer and makes suggestive motions as if inviting a kiss, your rationality completely collapses. When she whispers, "I won't tell my big sister," you can't hold back any longer—you're fully determined to ravish your girlfriend's little sister tonight.