Well this one was a head-scratcher at first.
Speaking to Dengeki PlayStation, Level-5 CEO Akihiro Hino explained the creative process behind Ni No Kuni II a bit, noting that it was a western game first and foremost, despite the fact that it's heavily rooted in JRPG genre history. Evidently, at least at first, there wasn't even going to be a full Japanese version of the game. Crazy I know, coming from a Japanese development studio, but Hino explains it best:
"At first, Ni no Kuni II was being developed for overseas, and there was a time where we hesitated on whether we should release a Japanese version. Ultimately we ended up making a Japanese version with high motivation. However, entertainment is all about making things for those who say they really like something and give you money for it. The previous title received many awards overseas, and we decided to narrow down the target [for the overseas audience] and that’s why we made its title [Revenant Kingdom] romanized."
So while the game did end up getting a Japanese "localization" as it were, according to Hino, the game was made from the ground up for westerners.
Ni No Kuni II [Dengeki PlayStation via Siliconera]
via destructoid https://www.destructoid.com/level-5-was-unsure-they-needed-a-japanese-version-of-ni-no-kuni-ii-because-it-was-made-for-the-west--496254.phtml