said that in one of his designs he used "minimal material to think about deeper space."
recently described his aesthetic like this:
You could say that my aim is ‘to recover the place’. The place is a result of nature and time; this is the most important aspect. I think my architecture is some kind of frame of nature. With it, we can experience nature more deeply and more intimately. Transparency is a characteristic of Japanese architecture; I try to use light and natural materials to get a new kind of transparency.
his firm's web site; my post on his private houses here.