As previewed yesterday, on the 28th—the last day of work—we offered kagami mochi at the reception counter of the Palaceside Building's west main entrance.
Since we had the chance, I reviewed the origins of kagami mochi. Rice originally held a special place in Japanese agriculture; harvest thanksgiving rites such as those represented by the Niiname-sai seem to have been performed since ancient times. According to an explanation by Professor Shintarō Niiya of the National Museum of Japanese History on the Japan Kagami Mochi Association website (http://www.kagamimochi.jp/saguru/page2-3.html), Murasaki Shikibu's The Tale of Genji contains the passage "even kagami mochi was brought forth... and celebrations were held," suggesting it was already well established by the Heian period. Wikipedia states that "it came to be offered in its present form after the Muromachi period, when homes began to have tokonoma alcoves." Beliefs that the spirits of the dead and ancestors visit at New Year, and vague hopes that the gods will bring good fortune in the new year, must have converged over time into the tradition of kagami mochi. Professor Niiya says the round shape is said to imitate the human soul (heart), and that it came to be called "kagami mochi" because mirrors of old were circular.
The date of kagami biraki (breaking the mochi) varies by region, but it is generally performed on January 11, after the New Year period (matsunouchi) ends on January 7. Because the divine power of the gods resides in kagami mochi, eating it is the point—to receive new vitality.
The Japan Kagami Mochi Association is an organization founded in 1972 by manufacturers of "integrated two-tier kagami mochi packs," aiming to spread kagami mochi and especially "to deliver new forms of kagami mochi that inherit traditional style while matching modern lifestyles." The kagami mochi placed at the Palaceside Building this time is also contemporary: the two tiers are packed as one unit, with pre-cut mochi inside so that after kagami biraki you can enjoy delicious mochi as is. Come to think of it, mochi once eaten only at New Year and special occasions can now be enjoyed year-round. I remember when I was a child, noshi mochi freshly pounded and delivered from the rice shop was so soft we could not cut it right away; a day or two later, when it had firmed up just enough, we cut it with all our might. I pushed down on the back of the knife with my left hand through a cloth until it hurt— all to eat the trimmings a step ahead of New Year as a reward. I fondly recall scraping mold off hardened, cracked mochi at kagami biraki with a knife, soaking it in water to soften it, and eating it as zenzai. Next year, I think we will properly stack mochi into kagami mochi at home.
The Palaceside Building will close the east and west entrances and the subway escalator entrance as on regular holidays from December 30 (Sun.) through January 3 (Thu.) (please check individual shops for hours after the 29th).
We wish you a happy New Year.