The Kingdom Hearts Memorial Ultimanium was released today in Japan along with Kingdom Hearts 2.5 HD Remix. A comment from series director Tetsuya Nomura was also included in the book, which has been translated below (credit to SQEX☆GAL for the translation):
Message from Tetsuya Nomura
If I had to pick, I am a person more on the dark side like Xehanort and co., I harness the burning anger in my heart into what I create. Kingdom Hearts III’s current development explodes very much in this sense. Each time, it’s a battle with Sora and co. who are the exact opposite of myself, it’s been over 10 years and yet we haven’t reached a conclusion.
This battle will surely last longer.
In Kingdom Hearts III as well, I am scheming many challenges that Sora and his friends must overcome, because I myself cannot lose either. And in preparation for the great battle that lies ahead, we have this one book that looks back on their entire journey.
When I think about it, I had an explosive mindset when I made the first Kingdom Hearts as well.
Thus when I look back at all the material, I feel that fever again. Fans who will continue the journey so far alongside Sora and his friends will also recall their own feverish enthusiasm. With that passion, we will not lose to darkness, and Sora’s journey will continue onwards.
The journey still continues, but I would be overjoyed if you stuck with us until the very end.
I certainly hope that “burning anger” refers more to passion than anything else. However, it could also be referencing his recent dismissal from his position as director for Final Fantasy XV.