I have a therory (SPOILERS)

[Purity Uchiha]

Okay, everyone was freaking out because Kakashi got the mangekeyo sharingan (in the manga) without killing his best friend. The argument is "He didn't kill Obito, so I guess Itachi was wrong about how to get it.". But, I think Itachi was right.

Does anyone know what happened to Rin? How did she die?
Perhaps Kakashi killed her accidently somehow.
ninja  

[imsohappy1]

Nope, i think there is another way to get the MS.

If he killed Rin to get it the it would have been befor the timeskip, or even befr the series began. Thats because he announces that everyone he ceares about is already dead to Sasuke befor his MS appears.

I disagree, but good theory though.  

[Le Marquis de Noir]

Well you notice, Itachi's mangekyou sharingan brings you into that starnge world. Kakashi's MS sends things into a different dimension, he does this to deidara's arm. I believe it is some strange one of a kind sharingan that only he has because also, it looks different from Itachi's MS, just a theory.  

[Samurai Senel]

Well my theory is Kakashi blames himself for Obito's death and they were best friends I'm guessing that's what unlocked it.  

[Purity Uchiha]

hmmm...the Kakashi blaming himself one is a good reason too...  

[nintendonerd]

My theory is the same as shikonookami.