I just read this fic and now I can't find it.

[glossedcurls]

It was a one-shot rated NC-17ish. Where Sirius had to prove himself to be a worthy mate of Remus' by having a sex marathon with Remus' wolf alter ego that Sirius called the "Wolf King" or something like that. In the morning, when Remus returned to himself, he was afraid Sirius would be upset with him for making Sirius submissive but Sirius was fine with it and the lived happily ever after.

Thanks in advance.