A growing number of foreign nationals in Japan are speaking out against what they say is a little-known but entrenched system that allows one parent in a broken relationship to take away children and block the other from visiting them.

The issue of what domestic and overseas media call parental child "abduction" has regained international attention recently, particularly in Europe where documentaries have been made about European fathers whose children were taken by their Japanese wives.

Australian Scott McIntyre was the latest foreign national to raise his voice against the estrangement of separated parents from their children in Japan.