Once married to Japanese women, they say they were prevented from contact with their children when their relationships disintegrated, sometimes even after court rulings in their favour.
Tough laws and patriarchal cultural norms that overwhelmingly see mothers granted sole custody after a divorce -- 80 percent of the time, according to official figures -- mean that fathers rarely see their children again.
Frenchman Emmanuel de Fournas has spent years battling for access to his daughter after his Japanese ex-wife moved back to Japan. Despite winning a court order in France and filing a case under the Hague Convention on the Civil Aspects of International Child Abduction in September , he is still fighting for the right to see his daughter.
AFP was not able to contact the mother.
His experience is not unusual. There is room to do more and better," says Richard Yung, a French senator who came to Japan to plead the cases of several French parents.
For foreign parents, most often fathers, "this poses major problems, because they have a different mentality and they can't comprehend losing custody or the right to visit their child," said Nahoko Amemiya, a lawyer for the Tokyo Public Law office.
Even when foreign parents win their case in a Japanese court, enforcement is patchy.
The State Department's report described "limitations" in Japanese law including requirements that "direct enforcement take place in the home and presence of the taking parent, that the child willingly leave the taking parent, and that the child face no risk of psychological harm.
Stephane Lambert spent years fighting to see his son after his wife and child moved away from their home in Japan -- a case not covered by the Hague convention.
Looking at a photo of him tears me apart. I've learned to forget him.
But regardless of changes to the law, the pain of parental separation is always traumatic -- as demonstrated by the case of Joichiro Yamada, who was 10 when his Japanese father and American mother split up.
I wanted to go back to my mother. A year felt like an eternity.