Unfortunately Japan has been lacking sorely when it comes to joint custody as there simply was none backed by any law which led to the large ammount of kids just disappearing with one of the spouse while the other was left with no legal options. For foreigners married to Japanese citizen this is a nightmarish scenario when dealing with divorce involving kids. Even though Japan signed onto the “The Hague” treaty… not much was done to pursue these “kidnap” cases.

NOW finally Japan is taking steps to abolish the single custody and introduce a joint custody system. Still allowing single custody in cases of abuse etc … but that speaks for itself.

https://www3.nhk.or.jp/news/html/20240130/amp/k10014340561000.html (In Japanese - use Google translate if needed).

As someone who has gone over “loosing the kids” scenario when getting divorced to many times to count as my relationship has been on rocky ground for last 2 to 3 years … it’s a absolute relief to read they are finally catching up to something that’s common sense in many countries.