Rins death / kakshi gains MS

[thegame]

Nope not important plot advancement only. The manga said she died later in the war.

Rin's fate after this was unknown at first. She is assumed to have died, as Kakashi has indicated that all those close to him were dead and the fact that he lamented on how he failed to protect her. This would later be confirmed during Kakashi's dying moments as he was going to see Minato, Obito, and Rin.[2]Narutowiki

But you never know I guess

My problem is, she clearly didn't die in the 3rd war. Of course she could have died afterwards on a mission, but I doubt that. It would make sense if she died in the time skip and that lead to kakashis MS, but it wouldn't make sense that we haven't seen her at all, or maybe kishi just hadn't thought about her till when he made kakashis gaiden

 

[Joki]

She was in the databook, it's not Rin, and she was in love with Hayate anyway. But yeah, Kishi should totally just retcon that shit and make her Rin. I love how the pages you posted still tie in with current chapter, about what Kakashi was saying about himself though.

 

[thegame]

why the hell would akatsuki waste their time to kidnap Rin to lure in a young kakashi who was no threat, and still wasnt a threat to their plans? and how would they know that kakashi in the future would be paired with naruto?

Well that was just speculations. I don't think they would kidnap Rin for any reason, if they did, but maybe just wrong place, wrong time.
I could see reason for Tobi to capture someone with informations on Konoha, maybe Rin was in ANBU which explains why we never saw her, capturing someone from ANBU to extract informations would be in favor for tobi, since he knew Itachi was still protecting Konoha and would not give akatsuki informations. Also we never heard much of any akatsuki spies in konoha.