I'm gonna lay down what I've found in my cyber sleuthing about Kawaii-Nudestuck.
Since the account closed a lot of stuff has come to light. First of all there is the tumblr account I'm gonna call Turdburgler which was found to be the same person. (this is not the real account name, I'm more interested in their privacy). After they were found, they started denying it for a while until eventually being presented with so much proof, they had to shut the nudestuck down. Reason being is that she was underage. And I'm not talking like, a little underage I'm talking like 13 or 14 underage. Turdburgler changed their Tumblr name hoping to get away from the controversy but after a while, they changed accounts totally.
See screenshot.
I was able to find the new account but for privacy reasons I'm going to not link that here. It's since died anyway so it's not worth finding. She moved to other websites under another name which I also managed to find. I found their Reddit account among other things where it's QUITE evident that they are now undergoing FTM hormone replacement therapy for what seems like a few months now? They have even changed their name legally by this point. So if you are hoping for more nudes out of them, that's what you are in for.
Anyway, it's evident the lengths they have gone to get away from all this and I've been careful not to give away too many details.Please don't go hunting to harass them, I was only able to find them thanks to a lot of obscure posts and cross referencing old accounts along with a few lucky guesses. They want to be left alone so let them. They were underage. Delete those images and move on.
TL;DR - They were like 13 when she made that account so 100% of them are illegal as apposed to the "rumor" that some of them are fine. They are also going through hormone replacement therapy to become a guy. No nudes from them ever again.