Yesterday, still bent on the idea of experiencing a really Japanese Christmas I went and bought a Christmas cake from the kombini, 7Eleven to be specific.
Japan seems to have two types of Christmas, the first being a form of the French Buche de Noel, which is a chocolate cream and chocolate sponge roll, iced and dressed to look like a yule log. The second is white cream and plain sponge layer cake, often covered in fruit or Santa themed decorations. The specimen I purchased was an example of the former, which I split with my colleagues. It was very sweet, light, and more creamy than chocolate-y. The idea of these cakes, is that it is to be shared by your family on Christmas Eve, and is often purchased on the way home from work on this day.
I didn't really stick to the tradition as I bought and ate mine on Christmas Day instead, but I don't think that affected the flavour at all.
All in all, the cake was pretty delicious, considering it was convenience store fare, it seems like an alright tradition to have for Christmas.