Many traditional customs are observed at the beginning of the new year in Japan. For example, entrances to homes and shops are decorated with the pine and bamboo kadomatsu decoration or shimenawa braided straw ropes, a custom with its roots in the Shinto religion. It’s also the time of year when people enjoy mochi soft rice cakes and osechi-ryori, the traditional foods associated with New Year celebrations. These customs derive from harvest thanksgiving rituals developed over the centuries by the Japanese, who were mainly engaged in farming then, and from ancient religious ceremonies. Each of these practices is imbued with meaning, and experiencing a traditional Japanese New Year will surely be the highlight of your stay.
Japanese New Year:
The Japanese New Year (oshōgatsu?) is an annual festival with its own customs. Since 1873, the Japanese New Year has been celebrated according to the Gregorian calendar, on January 1 of each year, New Year’s Day. However, the original celebration of the Japanese New Year is still marked, in Okinawa for instance, on the same day as the contemporary Chinese, Korean, and Vietnamese New Years.
Full detail: http://en.wikipedia.org/wiki/Japanese_New_Year