Tell me more! The Japanese have a custom of offering mochi (rice cakes) to the deity of the coming year’s harvest, or toshigami, in the New Year. Traditionally, neighbors would get together to make the mochi at the end of the year before. Few families today own the big mortars called usu that are used to pound the rice, but mochi-tsuki (rice-cake-making) events are often held at elementary sch..