Kagome and Sango are caught reading hentai manga by Sesshoumaru while Inu and Miroku are bathing. He becomes curious about it and steals it from them. Things happen and he starts to be interested in both of them. They go to the future and end up buying him some gay manga as a joke. He thinks that the girls are trying to tell him what they want in a lover. Kag and Sango end up fighting because of a misunderstanding about a "mighty member". Sess comes around to invite them both to his home so that he can begin to claim them. Since the girls are fighting Sango goes first and she ends up telling him that they are mad at each other. He and Sango leave to find Kag so that they can make up. Sess does this so that he can have both of them instead on one. It's an older fic and a lot better then I'm making it sound.

Hi, srry I actually don't know this one (though I did read a fic once that was Sess/Kag/San in the begining and then I think was going to become Inu/San and Sess/Kag but the auth never got around to continuing it. K that was off topic lol) but I just wanted to say I love Saiunkoku Monogatari too! It's awesome sauce XD

I found it !!!!!!!

It's called the Tale of Kagome on Media Miner

Here's the link if anyone was interested.
www.mediaminer.org/fanfic/view_st.php/130367