The location is in a high profile area of Tokyo, called meguro-ku and going there we have seen so many villas as never before. It is a bulding for apartment in a japanese style which means for Us, westerns, small and often low (see the floor plans here for specific areas numbers). This particular case has probably faced many restrictions since counterceilings are absent and on the top of your head there is a particular concrete wｈich resembles the one visible from this picture. Here below the assays of the dye before they decide.
An apartment was used for the explanation of the design process which took two years, and the exhibition of the modelling which is a sort of thing that mr.Hirataand his teammates are really good at.
The floor you can see is wood made, protected by a rough white hue. Here is another blog with better pictures than mine.
My unrequested suggestion is to be a bit more misterious about the process. For instance this concrete is really good. Maybe it is not so evident and clear how to reproduce as it seems, I would rather to hide the secret ot the making instead of expose it. Maybe somebody else would claim the copyright one day!
If you like to know more about the concept ofMr.Hirata, he pulbished a book called Tangling, written in japanese and English (the amazon link It is not a book for everybody, Leibniz and Newton are juxtapposed for instance.).
Also here a dense article that summarize his approach.