Kagami biraki means “to open the mirror” in Japanese. The mochi that was offered to Toshigami-sama as a Shōgatsu kazari is called kagami-mochi or mirror-mochi because of its shape. Usually on the 11th of January (the date may differ depending on the area) we eat this mochi, and the ceremony is called “kagami biraki” or “to open the mirror”. For this ceremony we are supposed to break it with a mallet instead of cutting it with a knife. Cutting is considered taboo because it has an association of seppuku or harakiri.