Carlos Bermudez comments

CH3CHO: "The definition of "kidnapping" is almost same as that of English law. Kidnapping is (1) the taking or carrying away of one person by another; (2) by force or fraud; (3) without the consent of the person so taken or carried away; and (4) without lawful excuse. --Wikipedia

So, if no force or fraud is involved or if the child gives consent, the carrying away is not a kidnapping. If you do not like this definition, tell so to Englishmen and women."

You should leave the interpretation of laws to people who know what they're doing. Children are not legally capable of providing legal consent. Until they reach the age of majority they cannot entire binding legal agreements.

CH3CHO: "If the child is a double national and one of the nationalities is Japan, surrender his Japanese nationality if you really do not want him affected by Japanese law."

So your solution to the fact that the inequities of Japanese law strip children of major parts of their identity, culture and heritage and patrimony... is to strip children of major parts of their identity, culture and heritage and patrimony? Brilliant.