You need mod for playing with this skin and actually complete the game in "Im The Night", that would be open after New Game+, completing "Im The Night" opens character trophy (Worst Nightmare). After that you get the opportunity to open this skin. The easiest way is download saves from the Internet to get this trophy.
You can find all other necessary information in this guide:

https://steamcommunity.com/sharedfiles/filedetails/?id=492615505

what?

how did you get this skin?

it's mesh swapping

well first u need to complete "Im The Night" diff u CANT have it if u dont the rest is easy

How do you get this!?