@Ddog123 its from the doujin ver nanashi made during his hentai years you can find it in here.
Though Nagatoro there is a lot worst especially the third part but if you want to see a bit of a proper progress the just skip chapter 3 you can also read chapter 3 first then start from 1
Its because for some reason she got worst at 3 even though she got better at 2 so the progress of Nagatoro’s slow switch to dere in 1 & 2 then back to being a bitch at 3 is kinda weird 4 is 80% dere. Then 5 is the oneshot I guess.