Mishima Yukio and English

I was really astounded to know that Mishima Yukio had a good command of English, English with slight English accent. As long as I know of Mishima, I have never heard that he had lived in foreign countries. As some of you guys know it, he was famous for his extremely nationalistic ideas. It seemed to me that all the interests he possessed at the time were Japanese culture and tradition, our Royal Family, Bushido stuff, and the like. So it is very surprising that he could speak almost perfect English at the time when there were neither so many English speaking materials or Nova.

Although I can't agree with his political views and his novels are not my cup of tea, I think that he was one of the most intelligent and the most interesting man back then. He was said that he loved to read Jean Cocteau and Oscar Wild at the age of fifteen. Unless you are either genious or crazy, how can you enjoy those authores at as early as that age?