Yasushi Horibe is one of my favourite Japanese architects, quite unknown in the west.
His work is not as abstract, and consequently not as photogenic or diagram-o-genic as SANAA or Toyo Ito or Sou Fujimoto. The physical act of building is clearly his focal point. He also has an affinity for elementary geometries, like the composition of square pyramid roofs above (he has also done houses based on octagonal, hexagonal, and pentagonal geometry, although I unfortunately cannot find any images of them at the moment). The spatial composition is not showy but rather simple, but in a typical Japanese fashion, impeccably considered, always right on the spot and with some ingenious twist here or there.
These are images I found by googling. I have to scan some more from the issues of JA/Shinkenchiku I have back home.
Here is a link to his website, if you can read Japanese or otherwise have the patience to navigate it. Unfortunately, the pictures are tiny, like they seem to be on most Japanese websites (why?).
UPDATE: here’s some scans from Japan Architect 67 (autumn 2007)