It would have sold terribly anyway
.

If Sony claims PS4 exclusivity for KH3 in Japan, does that also rule out an NX release is probably bigger question. Or is it just Square Enix who says fuck the 100k Xbox owners in Japan.

Move it to NX :P

NX on launch will have outsold the Xbox One lifetime sales in Japan, so NX does make more sense, but lets see what the NX is before we start wanting games on it lol

My guess is that NX being a hybrid will most likely catch the PS4 pretty quickly as well in Japan...

If the Rumours are true the NX will compete with the Xbox in western area's but be whiped out by the PS4, in Japan however, you are correct sir!
The NX actually seems like the ideal device for Japan, they even love the vita, and the vita TV did decent! and this is kinda like that but with better first party support (and prob worse third party :P) anyway, thats not the question, the question is can the NX easely handle a graphical game like Kingdom Hearts, only time will tell.

It has not been deleted, they only changed URL site recently and I guess they still need to update the Japanese Xbox site database. This is the new one:
www.xbox.com/ja-JP/games/KINGDOMHEARTSIII

This, however, is that the old one does not work anymore, but they still have to remove from the site:
http://www.xbox.com/ja-JP/xbox-one/games/KINGDOMHEARTSIII

You're welcome ;)

That settles it then

You'll be waiting for a while, sadly.