Mirrors 鏡, kagami, have a magical element to them in Japan. You see them everywhere at Shinto as well as Buddhist Shrines. I find them mysterious, beautiful and spiritual reflections of the other world. It was a mirror that lured the Sun Goddess Amaterasu out of her cave. Writers in Kyoto Founder John Dougill’s blog Green Shinto has an inexorable amount of information about them. I especially love the one about Queen Himiko’s Magic Mirror, a makkyo 魔鏡
Here is Sensei Masashi Nakamura’s answer to my question to him about the significance of mirrors:
“Why is a mirror enshrined in shrines? This proposition is very important. In this case, the mirror is called a 神体 – Shintai: deity body. The 神体 Shintai: deity body is a deity’s 依代;Yorishiro, but it is enshrined like a deity. 依代 Yorishiro is an object to which a spirit is summoned, or drawn to an object or animal and is occupied by a kami 神.
Originally before the construction of a shrine, the 依代 Yorishiro of deities were mountains and large stones. However, in the Meiji era, National religion of Shinto was re-established with Amaterasu as the supreme deity. Probably the mirror means Amaterasu and the sun. So, at shrines, mirror, one of the three sacred treasures of emperor, began to be enshrined as the 神体 Shinta – deity body.”
Naturally, that deity’s reflection is also YOU. We humans are a part of divine nature and a mirror reflects that divinity back to us. Tvat Tvam Asi, thou art that. I had also read on a omikuri from Sumiyoshi Taisha Shrine that a mirror is also a reflection of the health of one’s body.