When the temperature starts to go down, a Kotatsu is an essential item in Japan to get through a cold winter. A Kotatsu is a low table with heater installed underneath its tabletop. It comes with a Kotatsu Futon (heavy blanket) which covers the table to keep in the heat. You can control the temperature of a Kotatsu heater and also set a timer; so it will turn off by itself incase you fall asleep while you are sitting underneath its warmed blanket. Some houses have a “Hori-Kotatsu” which is a Kotatsu built into the floor of the house. When using a Hori-Kotatsu you don’t need to sit on your knees or cross-legged, you can sit just as you would if you were on a chair.
However, be careful not to catch a cold while visiting Japan! Thermostats are still not common in Japan, so Kotatsu’s are popular items. You can often see Kotatsu in Japanese dramas and Anime. Typical TV scenes featuring the Kotatsu are when people are sitting with their legs under the Kotatsu and eating a mikan (mandarine orange).
Kotatsu Heater (via Wiki)
Cats love Kotatsu! (video by shironekoshiro)
(video by mugumogu)