Hidan × Kakuzu Meta: TWO POORLY SOCIALISED CHARACTERS BEING POORLY SOCIALISED TOGETHER.

They're both very self centred people. Each man prefers the qualities in his partner which he also thinks are positive in himself.

Kakuzu likes Hidan's disregard for social bonds and persistent character (even though it annoys him to work around it) and admires his capacity for e-rated graphic violence. He clearly thinks of Hidan as a competent partner — that's why he's able to easily say things like "You're seriously underestimating Hidan," when Shikamaru draws him away from the fight with Kakashi.

I think Kakuzu also likes that Hidan is immortal. When he says that money is the most important thing, compared to bonds with other people or ideology, it's clear that Kakuzu has big problems with trusting the integrity of his interpersonal relationships. Aside from his off-screen history where his important social connections betrayed him (from his perspective), we can also extrapolate this from him being over 90 and still a ninja — most of his interpersonal relationships would have passed. Hidan could last forever, though, he's so poorly socialised that the likelihood of him making high quality relationships with anyone seems extraordinarily low. This is one of the reasons why Kakuzu likes his disregard for social bonds. It is way less stressful for Kakuzu to be attached to someone that cannot be forcibly taken from him, I think.

Even when Kakuzu says, like, we all die sometime, he's comforting himself with the impermanence of their relationship. He doesn't want anyone to take it from him but he also doesn't want to feel trapped by his commitment. What an exhausting man.

I think Hidan's feelings are a lot more romantic and poetic than Kakuzu's. He's a more romantic character. But they're still like... very similar.

Hidan likes that Kakuzu is an immortality trailblazer and looks up to him as an authority. He sees the things about Kakuzu that also exist in himself as beautiful: the deviations from humanity, the violence (even though Kakuzu uses it as a means to an end, and for Hidan violence IS the end), his capricious temper. Hidan has had few role models he really respects — that's why his entire history is very "abandoned his unworthy companions, sought inspiration in god, did some murder." He's poorly connected to other people. He relates strongly to Kakuzu because they're both bad at social connections, they share skills and some interests, and Kakuzu is older and provides a model of what immortality might look like in 69 years.

Hidan also trusts Kakuzu, which is interesting. He trusts him to let him take on fights, he trusts him to pick up pieces of his body and stitch them back together, and he even trusts his situational judgement — for example, when Ino is scouting for them, Kakuzu senses something and turns towards where he thinks she might be. Hidan clearly doesn't sense anything. But he immediately stops and waits for Kakuzu. He assumes, not that Kakuzu is jumping at shadows, but rather that he has spotted something that has escaped Hidan's senses.

Anyway.... hmm, how to wrap this up... oh, I know. Headcanon incoming: Hidan views Kakuzu's serial heart-stealing as his own little ritual. He's a bit patronising about how Kakuzu doesn't recognise it when it's soooo obvious to Hidan. The heart donor dies, and then Kakuzu carries their beating heart with him until it gives out or someone "kills" it, and then he also feels the death he granted them. Clearly a Jashinist ritual by another name.

ETA: I guess they also both think large violent men are hot. Like. Obviously. I don't know if Hidan is into the tentacles for like a deep psychological reason relating to his childhood or whatever... but he's definitely into the tentacles.