In the United States and Canada, Christmas is considered one of the single most important events of the year. However, in Japan Christmas is a much smaller holiday.
Growing up in the US, I was always excited about Christmas, because it meant that I would have time off from school and every three or four years, I would get to travel during the break. Here in Tokyo, only some international schools take time off and public schools take no time off for Christmas. Christmas is a working holiday and more of a shopping holiday than a cause for celebration.
People purchase Christmas cakes and fried chicken (often at KFC.) There is a belief that westerners celebrate Christmas with turkey which is very hard to come by in Japan, so fried chicken replaces it. Also, during the 1980’s KFC launched a massive advertising campaign that turned this into a national belief. Grocery stores start putting out brochures in November to advertise cakes you can buy. This idea comes from the fact that Christmas in the west represent Jesus’ Birthday and we eat cakes for birthdays. Christmas cake is a special type of cake similar to the white spongy cakes we call vanilla cake. It is normal adorned with frosting and strawberries.
When Christmas is celebrated, it is normally celebrated by couples on Christmas Eve. Basically a gift exchange, some KFC, and a bit of cake while hanging out or going on a date.
Christmas is a little overshadowed by the fact that December 23rd is the Emperors Birthday. Also, New Years on January 1st is traditionally one of the most celebrated holidays outside of possibly the holidays of Golden Week in May.