Ok so this fic was years ago and it was an AU between Sessho and Kags that is BDSM related. What I remember of it is Kagome finds herself on her computer late one night. She's lonely and horny and she comes across this site that promises to fulfill her deepest fantasy. She fills out the profile, adds a picture of herself and after a day or so she received a response. In her day life Kagome is a business owner working to enter into a partnership or contract or something with Sesshomaru who also runs his own business. Inuyasha is her best friend. She doesn't know that Sesshomaru is the guy she's been giving herself to as he keeps his face masked. I remember her getting tied across a table and being spanked, and then another instance where she insists on skipping one night because of her period and he won't hear any of it. He takes her to a public play club one night. She eventually discovers who her masked lover is.
That's all I can remember of it and I hope someone can help me. It was a very popular story. I think it may have been on A Single Spark