Genbu is one of the Four Symbols, the sacred beast governing the north. Commonly depicted as a tortoise entwined with a snake, it is linked to the direction north, the season of winter, and the black aspect of the Five Phases. Originating in ancient Chinese astral cults, it entered Japan from the ritsuryō era onward alongside Onmyōdō, astronomy, and feng shui thought. Adopted into castle, shrine, and temple layouts and rites as the emblem guarding the northern boundary, its form follows iconography; in local practice, the idea of directional protection often outweighs a distinct deity persona.