I don't know why, Japanese people eat mandarin orange in winter. I got mandarin orange from Ms.Saimu:) (tourist information staff)
Talking of Japanese winter, Japanese people like to eat mandarin with family at ※Kotatsu.
※Kotatsu...Table with an electric heater attached to the underside. This table has Futon (Japanese blanket) so, when you come in the Kotatsu, you will feel warm and comfortable.