Maybe what you mean every Japanese developer and Publisher (except Xbox and Nintendo games /exclusive) has become SONY second party. Then No one will argue, Period

its just that the Xbox One isnt successful in Japan

People don't understand that there IS money in exclusivity. A lot of money in fact.
Just because the term "competition is good" gets thrown around all the time doesn't mean it's 'law'.
square made a killing during the ps1 and ps2 days when Sony commanded the market.
It is just as fruitful to push one console over the top and forget about making ports, adding dev costs and time.

My take on this is that Square-Enix and Sony are the two companies that have the most interest in trying to revive the home console in Japan, while many other Japanese companies shift their focus to mobile (though, Square is also doing its fair share of this as well) and Nintendo continues to struggle in the home console space (though, they are doing fine with their handhelds, of course). In a sense, the high-budget AAA Japanese titles have taken the biggest hit, since they require home consoles to be prominent within Japan.

Both Square-Enix and Sony have a vested interest in seeing the PS4 succeed in Japan. From Square's standpoint, it may very well be in their interest for Sony to have a lot of market power in Japan as opposed to a more level playing field, especially with all the weird idiosyncrasies with Nintendo's products and the fact that third party games don't sell well on their systems. By that, I mean Square can probably make its games for less money and sell more copies in Japan if the PS4 is the dominant console.

I think Kingdom Hearts III and Final Fantasy XV were put on both PS4 and XB1 without any sort of timed exclusivity for PS4 because a) those games sell well in the West and b) Square didn't predict that the PS4 would do phenomenally well worldwide. If and when FFXVI comes out (I don't think it will be an MMO since Square doesn't want to cannibalize the revenue stream of FFXIV which is doing fantastically), I am sure we are going to see some form of timed exclusivity, similar to what we are going to see with the remake of Final Fantasy VII.

SE virtually said this. Why do we keep having tons of threads about this?

You forgot to include a Saga game for Vita. It was announced a while back. Doesn't seem to have any news though. Hopefully in TGS...

Yeah, finally Square Enix is coming back!!! And they support PS Vita!!!
Btw, you forget SaGa 2015 in your list (it is coming exclusively to PS Vita)!

Sony is really back so are the relations to developers

Sony was forced to do it. Like they sold even their main headquarter in Japan and laid off thousands of people. Despite the success of the PS4 Sony is in a desperate financial situation and is making big losses still.

Correction. They sold their OLD headquarter,and while they still struggle,they are on the right path financially. From last year until now,their shares has more than doubled in value.