I do not remember a lot but there are two scenes that really stand out. This first is when Sesshomaru and Kagome are in the forest. Sesshomaru is attacked by demons that want to take over the western lands. One of the demons has a sword that cannot be hit or blocked by another sword. I think it is called shadow something. Anyway, Kagome kills the demon with her sacred arrow and Sesshomaru goes over to her and put a courting mark on her neck in front of all the demons that were rebelling. This way they can know that he is able to “subdue” the Shikon Miko. The next scene I remebr is towards the end of the story, Kagome tells everyone that there are no demons in the future and sets up an alternate plane for them to live on. The land is accessed through a portal that is similar to the black pearl in Inuyasha’s eye

I'd like to read this if anyone knows what it is.

I kind of want to think it's this:
Fang's Master

But it might be this too:
Windows on the West

I know that the latter is rated MA.

I've read windows and it doesn't seem like that one. I'll check it out again though. I've not read fangs master but I'll give it a shot.

That doesn't ring a bell, and I've read both Fangs and Window ('course I could be forgetting something)

It's not Fang's Master (rated T). There's no courting mark and the only swords that are mentioned are the ones that belong to the brothers.

You are looking for Means to an End by Aiwendil Amaurea
m.fanfiction.net/s/1267700/1/Means-to-an-End

Fic rated M, no yims

EDIT BY WICCAN: This story is rated R on the Spark archive, so it would be MA here! If you want to read it there, here is the link: http://www.dokuga.com/spark/story/43/1