Hopefully this isn't one that I've already looked for, but anyways.

I believe it's an older one, The only thing I remember is that Sango and Inuyasha are in a hurry to get somewhere, it's raining and somehow Inuyasha loses control and mate's Sango in the rain, their both upset because Kags is with Sess and Miroku will never change his perverted ways.

Sorry I can't remember much else...

I don't remember a scene being in the rain, but Sango and Inuyasha do run off together in frustration and mate in a scene in Unworthy One, which is pretty old, but excellent read.

www.dokuga.com/spark/story/1349/1

Rated MA so no Yims.

Try The Price of Vengeance by Youkai Fate
SesshouMaru has always despised his hanyou brother and seeks to avenge the insults InuYasha has paid him. But is he willing to pay the price of vengeance? S/K I/S K/K M/K M/F Lemons NEW CHAPTER UP!
Posted : 2004-05-05 -:- Edited : 2006-11-11 00:00:00 -

Rating MA and unfortunately incomplete.

Somewhere around chapter 30, Inuyasha and Sango were searching for Kagome who was kidnapped by Sesshoumaru. Inuyasha goes all demon-mode after fighting with Sesshoumaru and mates with Sango. There may have been rain involved, not sure.

Thank you!! That's definitely it, too bad it isn't complete, great story!