Part of the problem is that Japan is not a signatory to the 1980 Hague Convention on the Civil Aspects of International Child Abduction, which works to ensure the prompt return of abducted children to their country of habitual residence. (international-divorce.com)
In addition, these cases often have a strong international law component: More than 80 countries, including the United States and most developed countries, have adopted the Hague Convention on the Civil Aspects of International Child Abduction, which requires that children who have been «wrongfully taken» or «wrongfully retained» overseas should normally be returned promptly to their country of habitual residence. (internationalfamilylawfirm.com)
Indeed, even if the conditions for an Article 13 (b) exception are met, the Hague Convention gives the court discretion to return the child to the country of habitual residence. (famlawconsult.com)