Honestly, I think this chapter lacks the quality of most of the other chapters. Maybe due that I find your explanation for Rin's disappearance to be not believable, not to mention you have not explain any connection to canon, where Rin died at Kakashi's hands.
Also, honestly, I think Rin does not help advance the story at all. With Tsunade, Shizune, and Sakura, you already have plenty of medics, so what purpose will Rin have in the overall story?
So in the end, adding Rin to the harem does not help the story at all. Heck, if you remove this chapter and just add the Mikoto backstory to other chapters, the overall story would be okay without the Rin storyline.
Anyway, I await the next chapter, especially Mikoto. :)