The hama is a ceramic support placed under pots when they are fired in order to prevent them from warping in the kiln. After one firing, the hama’s role is over and they are discarded. Since 1968 the Hamazen Festival has been held to conduct a ceremony of gratitude to the hama, and to foster interaction between the ceramics workshops and the local community. The term hamazen originates in the fact that the hama resembles a four-legged tray for festive food called ozen.

At the Pottery Shrine, Tōso Jinja, Imamura Yajibee, the son of Imamura Sannojō who established the Official Kiln of Mikawachi, is enshrined as a deity; the Imamura Family holds the Tōso Festival in his honor on April 15th. The Hamazen Festival follows in this tradition.

On the first day of the festival, newly made hama are offered to the shrine, and a service is conducted. During the festival period all the local kilns studios hold exhibitions and sales. Visitors walk around many historic sites and pottery workshops, and enjoy shopping for ceramics.