I walk near those premises when I go to work. I had come to notice it when I went for the first time to the Edo Museum which is quite nearby.
here is the link to the Japanese voice of Wikipedia, and here is the link to the NTT architect description. It is worth saying that this architectural office is doing great and well-pondered projects. The company has somewhere around 5500 employers!
This project features an impressive wall composed by louvre and I believe that was trendy when it was projected. I can not see anybody now, in 2014, doing a project using the same style.
The taste is somehow from northern Europe I would say, specifically Germany. ( I would not be surprised to read BMW at the top instead of NTT!)
I do not know who was in charge of the design but they did a great job.
My pictures are telling the truth about the coating that is unpredictable from a long distance point of view as it is too bold.
It is worth pointing out that NTT is the leader in the Japanese market of ITT. It might come from a monopoly, but I am not sure about that.
They are so big that they could afford to keep an internal architectural office of first class men as a matter of fact.
In this Japanese blog, there are more data about the construction company.