Sometimes I doubt that Hidan knows what love is.
I know- or at least, I knew at one point. The village stole that away from me when they locked me up. She chastised me for my failure along with all the others. It may be too late for me now, at this age, though I continue to prolong my life by stealing the organs of others.
By contrast, Hidan doesn't need anything to continue living. He doesn't need food, water, or air, only the curse that keeps him alive in his state. He's gone mad; there's no question about that. I doubt he can even distinguish between pleasure and pain anymore. His only guiding force is the god he made up to order him around when his village's authority abandoned the principles of death they'd drilled into his mind. I don't know much about it; I'm only aware of that because he complains of Yugakure's crimes against "god" frequently.
He infuriates me. I want to swallow his immortal heart and incorporate it into my own body, but his mutilated corpse would follow me around, bleeding out and shouting curses my way nonetheless.
Kakuzu ran his hands along Hidan's chest. It was cold- unnaturally cold for a human.
Are you even alive? Maybe this is just an illusion and you're a walking cadaver. A true immortal cannot exist in this world.
"Kakuzu, I love you." Hidan said confidently.
"You're useful to me, Kakuzu." I know that's what you mean to say.
"Do you really?" Kakuzu grunted in response. "What would you think if I died?"
"I'd think you were a damned idiot and that god's will was served. Of course, you'd spend eternity in Hell, as you deserve."
Of course. You don't really care about anything but your shell of a god. You needed something to grasp onto, and now you won't accept anything else. Kakuzu's expectations had been met. He felt he knew his idiot of a partner fairly well.
"Well, they say even Hell runs on money, so I'll be set for that 'eternity.'" The words were empty, made meaningless from rote repetition. Kakuzu didn't believe in a Heaven or a Hell. There was death and then there was nothing.
Why the hell won't you listen to reason even now? Kakuzu's eyes bore into Hidan's violet ones threateningly. Of course, intimidation never seemed to work on that man. Grow up. We all deal with hardships. Why are you the only one who has to cower behind an imaginary leader to move on?
Hidan was such a child. Oh, he'd learned enough about the darker side of the world; he'd been born and raised in blood, and he'd been forced to become a killer at a young age, a soldier for his village. But the light- love, peace, friendship, charity- was denied him, and so his sense of morality was irreparably skewed.
"Hidan, kill for me. You aren't unnecessary. It's the cowards trying to erase your purpose who are unnecessary. They need to receive judgment. Kill in my name. Douse the world in war and blood, my son." Hidan had felt god's words the day he left Yugakure in a wake of death.
He only told Kakuzu certain lies because he didn't want to risk losing him, neither the sex nor his invaluable threads. He liked Kakuzu's body- his stitches seemed to bleed intangible waves of pain even lying dormant against his tan skin- but he was the worst kind of atheist. Kakuzu was an unrepentant heathen through-and-through, and so Hidan believed that he must have subscribed to the secular philosophy of love. He was also certain that Kakuzu liked him at least sometimes (but he had a peculiarly inflated opinion of himself), and so he'd decided that he could persuade him not to run away by claiming to love him.
But even if it wasn't "love", Hidan paid more attention to Kakuzu than to any other human. He put effort into angering him just to see his reactions. Kakuzu was sexy, strong, and useful. Hidan put a great deal of faith in him; he didn't believe he could be killed in battle, but if he was, he'd be furious over it. Even though he wanted him to perish in Hell eventually, Kakuzu's death would faze him far more than any other's could.
At that point, Hidan had nobody but his god and Kakuzu, and Kakuzu had nobody besides Hidan. They were both closer with each other than anybody else, and their partnership suited them both in different ways. Though that relationship was inevitably flawed, neither of them would attempt to terminate it.