This certainly looks like x&x&x, but is there any indication this is a from a second pixiv account of his?
Nothing more than little hints. X&X&X has deleted all of his r-18 works and all three of the pics in that account are clearly his. At first, I thought it was just another one of those accounts that re-up pics they like, but I don't recall seeing any of these pics beforehand.
I'm just monitoring the account, to see if it'll upload different works, but it certainly seems to be his account for R-rated works. Ragathol and another artist (I forget their name) here does this, too.
Yeah, I've seen R-18 accounts. douji just made one, for example. But I've also seen artists that heavily mimic others. There's someone (not on danbooru afaik) that looks a lot like yamu_(reverse_noise) but focusing on PC-98.
This one does look a lot like x&x&x, but the nipples/areola on pixiv #54958534, at least to me, look a lot flatter than his usual style.