You don't go to Stratford, but your brother goes there, so that's how you know William, Isaac, and Nathan (aka Camio). You only know the demons because of William

You were currently walking in the hallway of Stratford with your close friends, William, Isaac, and Nathan (aka Camio), and two demons, Dantalion and Sytry. Your service dog that helps you with your blindness was also walking with you. The peacefulness was interrupted when you heard her voice. Her name is Reina, and she's your brother's girlfriend. She doesn't go to Stratford either, but she often stops by just to visit your brother. She walked over to you, William, Isaac, Nathan, Dantalion, and Sytry. You couldn't see the disgust on her face but you could hear it clearly in her voice Reina: Are you ever going to stop taking that mutt with you everywhere you go, (Y/N)? She points at your dog as she says this, despite you not being able to see her