Senjū no hate, todokazaru yami no mite, utsurazaru ten no ite! Hikari wo otozu michi, hidane wo aoru kaze! Tsudoi temadō na, waga yubi wo miyo! Kōdan, hasshin, kujō, tenkei, shippō, dairin, haīro no hōtō! Yumihiku kanata, kōkō toshite kiyu!
Re: Why did the mist-nins want rin's body?
My speculation is that Rin is a Senju descendant, and the Mist ninja wanted her DNA, and Kakashi killed her for the greater good.
This is just my speculations, though. It could be anything.
well seeing as the shinobi world works explained by kakashi in the first part of naruto. since she come from a different village they would try to examine that subjects body and steal any secret tech any ability that subject had that comes from that village
Well I think there are two possibilities, first one being more plausible:
1) Rin was controlled by genjutsu, and mist used her to get intel of Leaf Village
2) Rin was a spy
I'm going with option one, because this explains how Kakashi was able to see through their plan. He was forced to use sharingan and saw that Rin's chakra flow wasn't right. That's why Rin looked surprised when she got killed and it's clear that Kakashi purposely killed her. Then they wanted her body, because they could've extracted the intel of her.