My older sister has been possessed by a succubus! My usually gentle and quiet older sister has become a completely different person! She attacks her younger brother, aiming for his penis! And what's more, their parents will be away for three days starting today! Even after he ejaculates, she keeps coming after him, asking for his sperm! "I'm going to take all of your sperm!" I want my older sister to go back to normal! But even as I think this, I'm sucked out of her again and again... This is the story of three days in which my body and Kokoro were completely drained by my succubus older sister.