[aneki]

Well the Japanese mom should have thought very very well before deciding to move to Bumf*ck, Tennessee. Because US courts almost never grant full custody and rights to move out of the country to a parent.
Maybe she expected Japanese style custody, where one parent (mostly mom) gets custody and is free to go….?

It seems that they divorced and he married someone else pretty quickly. Mom agreed to stay in the small town in order to share custody. We don't know the details on why they divorced or if his re-marriage was the reason for it and what happened. We also don't know her situation - did she see a future for herself in Tennessee?

If the man you used to love once is now hating you and harassing you (that is what she stated once in court), and you live in the middle of nowhere in a foreign country and all you have are your children and you don't see them half of the time, I would probably also ponder this route she took, seeing there are big chances of getting away with it.

In general, it's very obvious that the country where the children are currently in will decide to the favor of the native parent. In this case, the father may be out of luck now.