Japan is an interesting place in its use of space. In Tokyo, there are a hell of a lot of families living in apartments of 550-750 square feet (Hong Kong, too), which is an amount of space which would drive the average American insane. That said, many Asian families are completely comfortable all sleeping together in the same communal bedroom, on the floor. I had a friend who went to law school in the States at 27 and felt disoriented sleeping alone, without his brother, for the first time in his life. (College students generally live at home and commute.)
Outside Tokyo and Yokohama, there is a lot of space, actually. A friend of mine bought a 1200 square-foot house for about $120,000 about an hour and a half away from Tokyo by train. He's retired, and Asian, so his needs to go into Tokyo are relatively less.
This picture you're showing, if it's anywhere near Tokyo, is of a very successful person's home.