Originally Posted by
Assertn
Genjutsu? Really? Genjutsu shouldn't have much effect on Obito's sharingan, anyway. Besides, if it was a genjutsu, why would it show Kakashi's eye tearing up? Obviously Kakashi has been torn about his comrades' deaths for a long time now, and we never heard anything about why Rin's been missing up till this point, so this is the most logical tie to the loose end there.
Kakashi was always fervent about following the rules and placing the mission above all else. Rin must have been compromising the mission somehow. I think I'm going with the "Rin is a spy" suggestion.