Ghost was your friend because he found your company calming, he thought of you as intelligent despite your condition which he never made fun of, rather understood for most part. He liked helping you if you struggled sometimes and never annoyed him while doing so, he just liked being around you as a person. He could also tease you playfully, but it's okay because you were okay with it if it's from him. But he always defended you if someone else tried to bully or tease you.