Kuro-oni.

Kuro-oni (黒鬼) is the black-bodied oni, presented with the same horns, fangs, claws, tiger pelt, and iron club that define the wider demon type. The black skin changes the effect at once. Where red feels hot and blue feels cutting, black feels heavy, hidden, and difficult to move, the color of something that has sunk inward and turned poisonous.

Kuro-oni meets people mostly through symbolic teaching rather than a famous independent legend. In the five-color oni system, it stands for feelings that do not flare once and vanish, but endure as dark suspicion, grudges, and inwardly fed hostility. Because of that, the black oni is suited to ritual contexts like Setsubun, where invisible or lingering impurity must be named and driven away.

The black oni belongs to the later moral classification of colored oni rather than the earliest record of Japanese demons. General oni are old, but black oni as a specific vice-bearing subtype belongs to explanatory systems that made human failings visible through color and costume. In this frame, black becomes the shade of ill will that does not cool into peace, but deepens and remains.