Genbu is the numinous beast of the north, Water, and winter, bearing the most singular form among the Four Symbols—the entwined form of tortoise and snake. This edition traces the meaning of that iconography and the notion of "land matching the Four Symbols" in Japan.

Its origin is in the stars of heaven. The chain of the seven northern mansions (Dipper, Ox, Girl, Emptiness, Rooftop, Encampment, Wall) likened to a tortoise wrapped by a snake is Genbu. The Huainanzi's "Treatise on the Patterns of Heaven"^[1] makes the emperor of the north Zhuanxu and its beast Genbu, assigning it to Water, winter, and the dark (black). The dark is the color of the Water phase, figuring the northern winter sky into which all things withdraw.

Two meanings overlay the tortoise-and-snake form. The first is the original sense—the figure of the stars of the seven northern mansions. The second is the symbol expounded by the Later Han Cantong qi^[3], which sees the entwined form of tortoise (longevity) and snake (procreation) as the harmony of yin and yang, female and male. The latter is an interpretation overlaid on the original sense, and the two must not be confused. Genbu, too, was anthropomorphized in Daoism into "Xuantian Shangdi (Zhenwu Dadi)," but this is a development of a separate lineage from the directional-guardian Four Symbols of Japan.

In Japan, Genbu was spoken of most concretely within the geomantic reading of "land matching the Four Symbols"—terrain backed by a mountain to the rear is held to be the auspicious position of Genbu. Yet the identification that "Heian-kyō is land matching the Four Symbols (the north, Genbu = Mount Funaoka, etc.)" is not a certainty from the time of the capital's founding, but a later interpretation organized and settled into doctrine around the 1970s, with even the identified sites differing among researchers^[6]. What is certain reaches only as far as the existence of the geomantic notion of "land matching the Four Symbols" in the Heian period. The Four Symbols' banners of the Shoku Nihongi^[4] are the literary first appearance, and the iconography keeps the tortoise-and-snake-intertwined form in the Genbu on the northern wall of the Kitora Tomb^[5].