This chawan is of the Ao-Oribe style, a sub-style of Oribe ware originating in Japan, commonly known for their striking asymmetry, bold brushwork, and use of rich green copper glaze (ao means green).
This bowl shows some of the noticeable traits in its spontaneous brown iron-oxide brush designs, and distinct green glaze accents on the rim and patches of the body, although the form is fairly symmetrical with a flared mouth and thin walls making it a hira-gatachawan (a summer teabowl)