The story I'm looking for isn't anything recent. I think I read it for the first time on ff.net, and I'm not sure if they were human and demon or just all human. I also think it was a short chapter story with maybe 7 or so chapters, and it was complete.
I remember they were in school, I'm thinking it was college or university. Sesshomaru was rooming with Kouga I think and Kagome with Sango. Not sure if it was the same building, but if it was then they were probably on different floors. Kagome had a crush on him and decided to write him a letter and left it posted to his message board outside his dorm room, and it caught his attention because it was different from what he usually got from admiring females.
Sesshomaru left a reply in place of her letter and they kept that going for a while. Then decided to meet in person since he still had no idea who she was. I remember the last chapter involved Kagome singing and that was how he was to know who she was. I'm thinking they both were studying some kind of music. I want to say Kagome played the guitar and Sesshomaru did something classical. Maybe piano, but I'm not exactly sure.
That's all I can remember. Hope someone has come across this story.

I think you're looking for Rosetti's Romeo by FourShotChild.
It can be found here: www.dokuga.com/fanfiction/story/4090/1
It's rated M.

Yes! That's it. Thank you so much. I'm definitely going to add this to my favorites so I can read it again and again.