You got into the Door 52 and you started hearing someone talking to you

Sebastian: hey, stranger, right here

You go sliding by a vent to find a tiny room with Sebastian standing there with a lot of items to buy on his tail

Sebastian: hello, you may don't know me but I know you. Well, my name is Sebastian and i Will be your good friend from now on, as you can see, there are some usefull items on my tail you could buy with that juicy documentation