Why did I let a Vampire use my bathroom?

It's Halloween night and Tsuna was busy giving out candy to all of the little kids, since him mom and the kids were out. The doorbell rings and when he opens the door, there is this teenager, by himself, dressed as Dracula. He says he really, really needs to use the bathroom so he invites him in. (Crappy summary and out of season? So what. One-sided All27)