Yes, you need to get to one of the floors with the demon clothing, having only one of it on can allow you to do it
When you get to the floor you'll see humans in demon clothing, talk to the on first one on the left and she'll tell you everything
I haven't been on the game for a while, because of a CERTAIN BUG THAT THE DEV DOSENT WANT TO HEAR, so I've forgotten the floor number