Japanese earthenware developed in the 4th century AD (during the Tumulus period) from the Yayoi ware of the preceding period. Great amounts of this everyday ware were produced into the Heian period (794–1185). A rust-red earthenware, haji ware is baked in oxidizing fires. Production began in what were then the provinces of Yamato and Kōchi and spread throughout western Japan, eventually reaching the eastern provinces. Haji ware resembles Yayoi pottery in its colour, shape, and lack of decoration. Shapes unknown to the Yayoi culture appeared in haji ware, however, such as small, globular jars and wide-rimmed pots. By the end of the 5th century, haji pottery was imitating sue forms.

Although the surfaces of haji pieces are finely finished, both their form and firing lack the refinement of Yayoi pottery, so that some haji pieces appear heavy and clumsy by comparison.