I was thinking Second Alliance by Imanijoan. I found it on AO3 and it says its Explicit there so I'm gonna go with highest rating here, no YIM.

Its been quite awhile since I read that one, but it hits a lot of the points, I can't recall off hand if the Kikyo part is in it though.

archiveofourown.org/works/4727579

EDIT BY WICCAN: Second Alliance by Imani Joain can be found here on Dokuga (http://www.dokuga.com/fanfiction/story/8948/1), and is rated MA, NO YIMs!!

Hi,
Your looking for healing carefully
www.dokuga.com/fanfiction/story/9378/1

EDIT BY WICCAN: Healing Carefully, by Caedes, is rated MA, NO YIMs!!

Hi everyone! I'm searching for a fic where Kagome is in Sesshomarus castle in order to heal demons. Its an illness or poison that is laced with reiki and youkai powers. Kagome tries to fix it herself but the youkai powers dont let her. It takes Kagome and Sesshomaru working together to fix them. At one point when they ask for the sickest patient its Kikyo who was turned into a demon.

Does this sound familiar? Thanks!!

Its not second alliance. I was actually reading that story when the memory of this other one popped in my head.

I dont believe its healing carefully either. I dont think it took place in modern times.

That sounds like Children of the Gods by K Rated MA www.dokuga.com/fanfiction/story/4509/1?author=7432

Children of the Gods was it!! Thank you Sarah!!