Translation of this book in English came out.
Takashi (Kei) Miyagi (born 1919) is the son of Goju-ryu founder Chojun Miyagi. He was a special advisor to JKF Goju-kai. He is not very well known in the international karate community but he had some publications in Japanese in the 60ies and 70ies. This is the translation of his first book written in 1968 I think.
I beelieve that he is still alive.

You can order the book through or via a link on (US) or via (Europe/Spain).

I ordered a copy last week, awaiting delivery later this month. It's rather pricy (99US dollar or 84 euro without tax and shipping cost) but it is sold as a collectors item, only 1000 copies available.