Are you thinking about investing in a Japan startup? Consider these tips from Tokyo-based angel investor Jonathan Epstein before taking the plunge.

Epstein has been investing in startup companies since 2001. He learned his trade from Softbank's founder and CEO, Masayoshi Son. Masa, as Son is often called, had made several billion dollars investing in Yahoo Japan, a joint venture between Softbank and U.S.-based Yahoo. He wanted to repeat his success by bringing other proven business concepts to Japan. Masa handpicked Epstein for that job from Softbank's California subsidiary.

Epstein had come to work for Masa in a roundabout way. Over an eight-year stretch, he zigzagged between jobs at well-known companies in Japan and the United States. Along the way, he picked up the Japanese language and an MBA from Harvard Business School. His big break came one day while working at a subsidiary of Softbank in California, at a time when Tokyo was actively buzzing. Masa told him, "Starting Monday, you're based in Japan." Epstein replied, "Yes, sir!"