Most fans wouldn't take Dx2 cameos so seriously on a writing aspect (and I wouldn't argue against that either), but this particular dialogue made me intrigued on whether the writer in charge was following actual directions or if they just happened to unintentionally misinterpret how Nanashi's dyed skin looks to other characters.
As far as SMTIVA goes, his green markings are not supposed to be seen (by normal people at least).
Notice how, compared to Demi-fiend, Nanashi didn't have direct comments on his "under Dagda's possession" look even from people that were familiar with him previously. Asahi didn't seem to be thinking of his appearance even in the one occasion she was about to point out a discrepancy
The possibilities behind their visibility in Dx2 that I can come up with are: a) the characters in question were exposed to the supernatural enough to see through them; b) the markings were intentionally made visible by someone; c) this isn't Nanashi per se but an entity that looks and behaves "like Nanashi" so the rules behind his circumstantial tattoo wouldn't apply.
Well... these are guesses from a player's perspective at the end of the day. Now I can't help but wonder what is the official view on this matter. At any case, the most interesting part of Nanashi's transformed design has more to do with his zombie-like state than how his green markings are perceived
