Kokûzô is a bodhisattva (J. bosatsu) with merit and wisdom said to be "as broad and boundless as the sky (J. kokû)." He bestows these virtues on various people and grants their wishes. In Esoteric Buddhism, Kokûzô serves as the principle image of rituals aimed at fortifying memory (J. gumonjihô) as well as those concerned with merit. The iconography of this deity varies according to the ritual in which it was used, and it is clear that the Tokyo National Museum piece was a principle image for the latter type of practice. The bodhisattva is depicted seated upon a lotus dais within a large circle of light represented as the moon. His right arm is suspended, with the hand held in a gesture (Skt. mudra) suggesting fulfillment of wishes (J. yogan'in), while his left hand holds a jewel in front of his chest. There are five buddhas in the jeweled crown upon his head.
The bodhisattva's body is white, bounded by an exceedingly fine vermilion line, and shaded with light vermilion. Subdued tones of blue, green, ochre, vermilion, and other colors have been applied to his robes and the dais, as well as to the crag and water below. Silver paint and cut gold and silver leaf (J. kirikane) further embellish the moon, the bodhisattva's mandorla, the canopy, and the landform. The sober style of this painting accords well with the expression on the face of the deity, with its downcast eyes depicted in slightly modulated line. The effect of the whole is one of elegant refinement and profound mystery.