Japanese house slippers are called Uwabaki (上履き) in Japanese which is hard to pronounce unless you can speak Japanese.
The Japanese usually wear those house slippers in schools, homes etc.
Some public buildings and other companies in Japan prohibit street shoes for some reason and they make you wear Japanese House slippers in those places if you want to enter.
Actually I would find that house slippers would be much more comfortable anyway although I prefer to either just wear my socks or just go barefoot in my house.
In winter I prefer to wear my socks even though I keep my house pretty warm in the winter.