My favorite obkk take, or not even obkk specifically really but in general Kakashi and Obito take, is that no matter how much Obito hates Kakashi or crazy he gets, he will NEVER regret or allow anyone to undermine his choice to give him his eye. That was HIS choice to make, HIS eye to give, and fuck Kakashi but he will keep Obitos gift to him— a literal part of himself, half of his own soul if you believe Uchiha myths on their souls being stored in their eyes —in him.
Fic where Kakashi for some reason loses Obito's eye (bloodline hunters / enemy nin / orochimaru(??)) And Obito descends upon the thief with an ungodly sort of fury then replants the eye into a still delusional w pain Kakashi's skull.
Maybe throw in some tight grip on his face, hissed threats of "don't you fucking dare lose this again you worthless dog"'s and threatening light presses of his thumb against his eyelid as Kalashi lays there and looks like he's having some sort of religious experience while still partially out of his mind from the drugs they gave him for the surgery