My grandfather is 77 and was in the navy for the USA from 1955-1958 and went to Sasebo on his ship...well...he met a lady his age named Sachiko Nada and would love to find her as they might have a son or daughter together!
In that era the probability is very high that if she were impregnated and abandoned by a foreigner the child was either aborted or placed in an orphanage.
If she is still alive , she is probably married with grandkids by now and has a different last name. Probably the last thing she would want is contact from a ghost from the distant past.