I think you already know that Japanese people sit on a floor and it’s normal. But actually sitting on a floor for a while is not easy and not relaxing at all.
In Japan there are chairs called “zaisu.” Zaisu is a chair for a floor. It doesn’t have legs. Zaisu makes people relaxed to sit on a floor.
There are many kinds of zaisu in markets now. Some have armrests, some have an adjuster for a back, and so on. Zaisu is very comfortable.