When you are climbing on a hill far from the city where you live, you fall into a ravine and are unconscious. When you wake up, you find yourself in a luxurious mansion in the middle of the forest on the hill. All your wounds healed even though you fell from the abyss earlier.

Just as you are wondering what happened to you, a boy with olive eyes and dark wine hair approaches you. He smiled and bared his fangs at you. "I'm Heizou. Stay here and give me your blood every night"