Kagami Mochi is a traditional Japanese New Year decoration, meant to bring good luck and prosperity in the new year. Kagami Mochi first appeared in the Muromachi period (14th to 16th centuries) under the name kagami (mirror).
It consists of two rice cakes (mochi) of different sizes, the smaller one placed on top of the larger one, and a Daidai (a type of Japanese bitter orange) placed on top.
Kagami Mochi literally means “mochi mirror,” and the explanation for this name is that the shape of the two mochi dumplings is similar to the shape of the copper mirrors used during the Muromachi period. In addition, the mirror has a very important meaning in Shintoism, as, along with the magatama jewel and the sword, it is one of its three sacred objects.
The two mochis represent the past year and the year to come. The kanji for daidai is 代々, which can mean (generation after generation), so the daidai symbolizes the continuity of generations and long life, while the mochi symbolizes the past year and the year to come. Thus, the Kagami Mochi symbolizes the continuity of the family through the years.
Traditionally, Kagami Mochi was placed in various locations throughout the home. Today, it is usually placed on a household Shinto shrine, or placed in the tokonoma, a small, decorated alcove in the main room of the home.
Kagami Mochi are usually made for decoration from December 28th until January 11th (or the second Saturday or Sunday in January) when a ritual called Kagami Biraki (the opening of the mirror) takes place, the first important ritual after the New Year. On the 11th, the Kagami Mochi is broken into pieces and cooked, either in a vegetable soup or in an oshiruko (sweet azuki soup).