Got you!
As far as I know you have to act cold and distant towards everyone since day one (obviously avoiding dead endings) til day five, also you gotta be creepy by choosing options where MC encourages Ren's behavior, or enjoys other's suffering. You'll know you did it right when Moth leaves you alone in the street to get into a random store on day 5 (Ren should not be there bcs you asked him to leave at the beach). Hope this helps you unlock it!