Itachi was different from any other partner he'd ever had.
Itachi made him think and feel differently, see things differently, act differently. Itachi forced him to question his own thoughts and emotions, his own instincts and upbringing. Itachi made him think too hard, and too inconclusively, about who and what he was, and where he had come from. He didn't particularly enjoy it.
If he had been anyone else, if Kisame had spent any less time with him..... He thought that he would have killed Itachi without a second thought.
He would have disposed of him, relieved himself of what promised to be an immense burden, an albatross around his neck once Itachi's vision and health deteriorated past a certain, useful point. Blind shinobi were quite simply a liability, not an asset, even moreso than sick ones. Vision was extremely important in a fight--that was why so many of his ilk favored jutsus that brought rolling forth the thick, obscuring mists of their homeland. They knew how to fight in it, as so many did not, and that was their saving grace--in Kirigakure on a bad day, every shinobi was nigh-blind. Konoha, on the other hand, was a land of eternal spring and sunshine, where the sky was clear and blue, and the sunlight blazed overhead, bright and hot and quickly burning away natural mist that dared to show its face for any length of time. Their land was a land of clear eyes and endless vistas, of peace and abundance and softness. They no longer knew the harsh realities of war as keenly as they should.
The harsh reality of war, of battle, of blood and death and destruction, was that you couldn't afford to let your heart rule you. Such was life--any vulnerability, any weakness, any exposed point of softness could be attacked and exploited, used and abused, broken and turned against you. You couldn't afford to be sentimental, or to care too much about your comrades. You couldn't afford to not kill as swiftly and mercilessly as you could. Because someday, someone stronger than you would come along, and all your work would be for nothing if you couldn't do what you had to do before or better than they did. Caring too much about someone, befriending them, coddling a comrade who would only slow you down and not pull his own weight.... That was unacceptable, inexcusable, intolerable. With any other partner, Kisame knew he wouldn't have hesitated to cut their throat or pierce their heart--it would be a quick, merciful death, a fitting end to a tool that was no longer of use. A gentle and respectful farewell to one he had once fought side by side with and cast his lot with.
And there was a time when he would have thought of nothing else, where not doing this sensible thing would have been literally unthinkable. There was a time when he had been immersed in blood and battle, war and glory, when the tenets of his village had shaped him almost utterly into who and what he was. (Death before dishonor!) There was a time when he had loved nothing better than his culture, his land, his people, his leader--when his young eyes had rested with awe and adoration on his Mizukage, his master, his Madara, who had seemed to him the most beautiful, powerful, worthy man in all creation, a god-prince destined to lead Kirigakure to glory. (See me, hear me, accept me, guide me. All I ask is to stand by your side always--only this. Let me serve you, and I will never want for anything more.)
But Itachi was nobody if not himself, and they had been together for nearly a decade, now. Itachi was a fascinating person, a man with hidden charisma, one who drew others--or at least, Kisame--to himself without even seeming to want to, much less try. It was difficult not to get attached, when you were all but raising a person--perhaps once he had been a child, but he had not quite come to Kisame as one, though nor had he quite come to him as a man--through their adolescence and into adulthood. They had worked together for perhaps a third or so of his life, and nearly half of Itachi's. He couldn't help but care.... even if everything he knew, all of his training, all of his instincts urged otherwise. In the end, sickness and blindness or none, what it came down to was simple faith and loyalty, trust and compassion. He could not, would not turn against this man whom he had shared so much of his life with. It was as unthinkable as not doing so would have been, at one point--he would sooner be capable of swimming unharmed through lava than that kind of betrayal.
As a Mist-nin, he was failing to do his duty--as a friend, he was doing what he could to help compensate for Itachi the more he deteriorated.
Kisame walked ahead of Itachi in the crowds, using his bulk to part them, to leave a clear wake for Itachi to walk through. Kisame had silently, subtly started shifting their habits more towards staying in inns, rather than the forests, or even going out to eat--crowds and unfamiliar terrain weren't things he wanted to deal with, with Itachi in tow. Kisame had learned to never move anything Itachi set down, to hand him things he needed before they were even mentioned, to always make a little noise when he walked. He finished fights quicker these days, toyed less with his opponents--he liked to get finished now, to make sure Itachi didn't need help with the mop up. (He seldom ever did.) The casual hand resting on Itachi's back or shoulder could easily be used to steady him, and offered an easy, natural support to lean against, should Itachi need it. He hardly even faltered in his stride now, even if Itachi exhausted himself to the point of near collapse--the most he did was scold Itachi about overdoing it, and warn him (again) about how it wasn't healthy to go to such lengths. Commentary on his actual condition had stopped entirely by now, even if he had to carry Itachi outright. (He was light as a feather these days, far too much so for comfort; he needed more protein to maintain his muscle mass, in Kisame's opinion.)
And when he did collapse.... well, Kisame couldn't do much more than worry. He could get Itachi to a bed and keep him comfortable, bring him food and medicine and help keep any fever down to manageable levels.... He could, in short, give Itachi as complete a day of rest as he could manage before they had to get on with their lives and their missions, and pick up as much of the slack for them as possible. He could work for him, worry for him.... and watch for him. He could watch him as he slept at night, chair against the wall, sitting at an angle to survey the whole room at a glance and ensure that the doors and windows were securely trapped, that they would not be disturbed until the sun rose.
He could hover his hands a hair's breadth over Itachi's skin, feeling the tingling hum of chakra coursing through his fingers as he modulated its flow just so, syncing himself with Itachi to feed it into his chakra channels without any telltale disturbances that might wake him up. (It wasn't so much that he didn't want Itachi to know--but he needed his rest, and Kisame hated to interrupt that.) If he didn't know Itachi's chakra, after all, then he didn't know his own--and he knew his own chakra very well, its flow and its limits and exactly how to nudge its currents and tides into order--where once it had run wild and free for lack of discipline, struggling to tame himself had actually given him far better control than most had, just for how much experience he had gotten. He knew himself and his own chakra, and he knew Itachi and his chakra, and it was no great sacrifice on his part to give a little of himself every so often, to help strengthen Itachi's body and keep the illness at bay as well as he could.
Throughout it all, he still tried to justify it, if only to himself--Itachi was a valuable man, a holder of an incredibly rare doujutsu, with amazing prowess. He was worth too much to kill right off. He was still too useful--the deterioration hadn't affected his fighting abilities that much, or that often. Not enough for him to be a burden. He was useful, he was worthy, he was valued, he was cared for, he was not a liability or a burden, he was adjusting just fine, better than fine, Kisame could compensate for him.....
Not yet.
Kisame had seen his share of people die in his lifetime. He didn't want this one--didn't want his partner--to die just yet, by his hand or anyone else's.
He wasn't ready.....
He should always be ready; Death waited for no man. Damned Leaf Village and their sentimental bullshit. This was all Itachi's fault, coming from that village and affecting him like this.... Obviously he'd spent enough time with the guy to be corrupted a little. Tainted by their thought patterns. Poisoned by their beliefs. It was disgraceful, really--any self-respecting Mist-nin should have been ashamed.
.....Yet somehow, in the end, Kisame didn't mind as much as he'd thought he would.
[Kisame shifts and stirs a little, but doesn't wake; his expression is peaceful enough, even content, as he drifts back into a deeper sleep. The Hitomi films for only a minute or two before shutting itself off, leaving him to see any comments made in the morning.]