I'm trying to, but I'm getting tired of asking questions and getting useless replies.
To search for him, we need whatever information you have. Simply telling us you have something doesn't help us.
Have you tried writing to the address you have? Are you sure he was really a doctor? If so, you might try contacting the Japan Medical Association.
Japanese names can be written in Japanese characters many different ways, so if you have anything from him written in Japanese, send me a photo or scan of it. (Send via private message).