So, there was a fic I read years and years ago when I first got into reading fanfics. It wasn't on FF, MediaMiner, AFF, Tumblr, or Wattpad. It was on a site I am 90% certain is "Internet Archive"... which doesn't exist anymore--but *maybe* it was posted here or on one of those other sites. This was before I discovered any of those, or Dokuga.

It's a one-shot smutfic, so NSFW (no YIMs!!).

Here's what I remember about it:

Kagome has made some kind of elaborate plan to have sex with Inuyasha in the woods. She left him a note professing her love, yadda-yadda, with directions of where to find her.

She's made this picnic set up somewhere, with champagne and food, but it takes Inuyasha so long to find the note that it gets dark and she can't see. She's had like all of the champagne by that point, so she's kinda tipsy.

So then someone she thinks is Inu finds her finally (but it's actually Sess), and she makes a move on him and they have sex. And it's not revealed until Sesshomaru speaks at the end that Kagome realizes what she's done. (But she liked everything--it's not noncon or anything, more dubcon)

One specific thing I remember is that "Inu" urges them into a 69 position during the foreplay.

Aaaand that's all I remember. I hope someone can find it. If not, it must be lost to time. <3

I think I remember seeing something like that on here. If I am thinking of the same one it was a Christmas fic, possible a striptease to santa baby? I'll look for the one I'm thinking of and if I find it you can tell me if that's it.
Found the one I was thinking of on Spark. Now that I looked over it again I don't think it's what you were describing, but if you want to check it out its Santa Baby! by Sesshomarei would be MA on Dokuga
www.dokuga.com/spark/story/5697/1