Kagami-moti is the rice cake which is display on Tokonoma, little alcove of each homes on Decenver, and eaten on January in Japan. Kagami-moti is made roundly like mirror as this name demonstrate. This is because, mirror was very important treasure in the past and it means mirror good thing or good examples, so people in those day follow this meaning.
In addition, Kagami-moti is treated as the thing to share between god and human being. We can eat that valuable rice cake and it is the thing to be very happy.