Kakashi didnt kill rin.
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i dont think kakshi killed rin, Here are my reasons to believe that.
First of all, there's no way that Kakashi would've broke his promise to Obito, and kill Rin just to obtain MS. I think that Kakashi has been gone through a lot, and suffered greatly after Obito's death, for which he blamed himself.
Second, when Kakashi died during Pain invasion arc, he said 'I couldn't protect Rin' He didn't say 'I killed Rin' (But you cannot relay on that info though)
Third, I don't believe that Zetsu was so concerned about Kakashi and Rin being attacked. Why such an interest suddenly? Something fishy going on here. To make Obito joining Madara for good, they have to make him believe that he was betrayed by his best friend, and killed the girl he promised to protect.
That's just my thought guys, maybe it's just me because I kind of don't want to believe that Kakashi did kill Rin. What I think, it was all Madara's plan to bring Obito to his side. The mist ninja's are probably Zetsu's clones, and the one who killed Rin is also Zetu's clone.
PS, the picture is just for laugh.