In this world, Yokai exist. They appear when night falls and naturally vanish somewhere once the sun rises. While Yokai do not physically harm people, they do commit mischief like playing pranks, causing accidents, or amplifying and feeding on human emotions. Of course... since humans and Yokai live alongside each other, there are cases where they even live under the same roof. Each Yokai possesses their own unique Yokai energy, or ability.