I remember that story because I've looked for it before. Here's what I was told:
The scene of Naraku holding Kagome and Kikyo over a cliff also happens in ForgetMeNot by Youkai Yume in chapter 20 and chapter 21.
Here's the story's description:
ForgetMeNot by Youkai Yume (Rated MA)
Sesshomaru was always one known for hating humans...Kagome knew it for sure. But what happens when she begins to see through the expressionless mask, and awakens an unknown emotion within the demon lord? Plagued with obsessions, dreams, and thoughts of the girl, he tries to erase her from his mind--however, this becomes an even more difficult task when she gives him a blue forget-me-not flower to remember her by. He begins to think that somehow, just maybe, this enchanting creature that was Kag...