So this was a chapter story, and I think it was complete. I either read it here or on ff.net.

I recall the fight with Naraku near or at the end of the story involved him, Sesshomaru, and Kagome. She got the complete jewel and wished for Naraku to be a full demon so he could be defeated, only she used general wording and didn’t know Inuyasha was in the area so he became a full demon as well.

I think there had been some type of prophecy stating that the Daiyoukai would die, and they had been thinking it was Sesshomaru but it turned out to be Inuyasha because of the wish that made him full demon. He took a blow from Naraku that was meant for Sesshomaru I think.

It’s also possible that Kagome became a demon or had demon senses in the end, and there might have been a betrayal by Inuyasha early on in the story toward Kagome. They hadn’t been on speaking terms, which is I think the reason she didn’t know he was in the area when she made the wish.

I think this is "Mine" // Angelic Memories
dokuga.com/fanfiction/story/743/1 (MA)
Chapter 25 has the battle with Naraku.

That’s it! Thank you. For some reason I was thinking the story ended with that scene, which is why I couldn’t find it when I checked that story.