I'm not entirely sure who did the work of editing, but as many of you know, Nanashi is/was a very prolific hentai artist and has done many far more lewd series than Nagatoro. My understanding is whomever made these edited images found appropriately sized and angled nipples from Nanashi's other works, plucked them out, and pasted them on Nagatoro where they fit. So it's Nanashi's art, just cobbled together from two or more places.