BRIEF DESCRIPTION: The following description is based on the original description by Nagasawa and Hongo (1984).

The cap of A. hamadae is 45 - 70 mm wide, yellowish-brown to brown or olive-brown over the center, grayish yellow towards the margin in maturity, light yellow to yellow around the margin when young, campanulate at first, then becoming convex to planar with a significant umbo, subviscid when moist, with a strongly sulcate-striate margin. The flesh is thin, white, yellow under the cap skin.

The gills are free, subcrowded, 4 - 7 mm broad, whitish, becoming somewhat pinkish with age, with a yellow subflocculose edge. The short gills are truncate.

The stem is 100 - 130 × 4 - 10 mm, slightly tapering upward, hollow, sulfur yellow to light yellow or grayish yellow, except for the lower third which is tinged with salmon color, and fibrillose-scaly except for its bottom-most portion [Note: illustration shows decoration is in a pattern often called zebroid, flame, or snakeskin.]. A bulb and ring are absent. The saccate volva is 20 - 40 × 15 - 20 mm, membranous, attached only at the very base of the stem, with a light yellow tint in the upper part of the limb, and with a fringed internal limb. The flesh is thin, white, yellow under the skin, pinkish at the base of the stem.

Odor and taste are indistinct.

The spores measure 10 - 12 (-13) × (7-) 7.5 - 9 (-11) µm and are broadly ellipsoid to ellipsoid and inamyloid. Clamps are absent at bases of basidia.

This species occurs alone or in groups in association with Abies-Castanopsis forests, especially under A. firma and was originally described from western Japan.

While the colors, spore shape, and habit of the present species suggest a relationship to the Slender Caesars (stirps Hemibapha), this relationship cannot be close because this species lacks a ring and lacks clamps throughout the fruiting body including the basidia. In addition, assuming that the illustration of the basidia and subhymenium is correct, the subhymenium is not composed of layers of roughly globose cells as it is in stirps Hemibapha.

Among the known taxa of stirps Hemibapha having spores approximately equally distributed between broadly ellipsoid and ellipsoid, Amanita hamadae is the only species known without bright colors except for A. hovae Bouriquet, a little-known species from Madagascar.