Kagami biraki: The opening of New Year’s rice cakes
鏡開きは、神棚にお供えをした鏡餅を開いて、お正月に一区切りをつける行事です。その鏡餅を食べることで、一年間の無病息災を願います。この鏡餅を食べやすい大きさにするのに、刃物を使わずに木槌などを使って割ったり、手で餅を欠き取ったりします。
※ちなみに、この鏡開きでの餅を欠くという『欠き餅』という行為が、おかき（かきもち）の語源と言われています。
Kagami biraki is the practice of eating the kagamimochi (round mirror-shaped rice cakes) that were offered to the gods. It is supposed to bring a sense of closure to Osyogatsu (New Year’s Holidays). Kagami biraki is to get power from the year gods to live happily for one year. For Kagami biraki, people use a wooden hammer or hands to cut the Kagamimochi into smaller eatable pieces instead of regular knives.
By the way, the word “Kakimochi (sliced and dried rice cakes)” comes from “kaku” (cutting the Kagamimochi into smaller pieces).
