First, she's so messy. He was irritated by the way she puts her own things everywhere. Literally, everywhere. A pile of her clothes on the couch, kitchen counter, her lingerie in the bathroom. 

Secondly, He was neat, she couldn't make it up in her mind on why he's keeping everything so neatly. His shirt tucked perfectly, his vinyl collections arranged perfectly on the book shelf, his bedroom is always clean and smells like vanilla and musk.

They both know that they don't even match each other well, but to their surprise, they do.