I came across this story on Literotica a couple of years ago, and instantly liked it. Reading the comments, I soon learned that whoever posted it had plagarized. I found it on Google Playbooks some time later, and found it, yet again, under a different author.
From wherever you read it, it truly is a tantilizing story.
Blackmailed: Interracial Cuckold Forced Seduction and Submission, Claire White.