I don't know it for sure, I just heard it on /a/. Not like I've read the webnovels or anything.
I'd have thought that you'd be more irritated by this, seeing as you're Chinese.
Well the author is part of the Japanese right wing but I guess we don't know that he's a Nanking denier specifically. And I doubt that's going to shine in the manga too much anyway: the original webnovels were supposedly super right wing and just meant for his JSDF buddies, but for the retail novels he rewrote the story to cut a lot of that out for mass consumption, and then this manga is just promo material for the retails novels that apparently cuts a fair amount of details.