Because Japanese house is traditionally built to be able to pass winds for natural wind cooling in summer. It was fine for summer but bad for winter, so we love

Because Japanese house is traditionally built to be able to pass winds for natural wind cooling in summer. It was fine for summer but bad for winter, so we love Kotatsu. Now, we can't live with natural wind cooling in summer (A/C is the only option), it's bad in both summer and winter.