Naruto Shippuden Episode 263: The Flaw in the Edo Tensei
Deidara blows up Shin using the explosive clay hidden in his body, with Kankuro’s hidden puppet only barely able to dampen the blow. As Shin’s body reforms, Deidara mentions that he will blow up his body as many times as he needs to in order to kill them. Sai manages to find the resolve to battle Shin and end the fight that started back when they were in Root, but Shin’s body starts disintegrating, his soul having been freed from seeing Sai’s completed picture that he promised to show him. Elsewhere, after Kankuro manages to capture Sasori and Deidara, Sasori’s soul is also freed after realizing what a true puppet master is, and he entrusts his Father and Mother puppets to Kankuro, making him promise to pass them on to the next generation when the time comes.
Kabuto’s reasoning behind leaving the reanimated corpses with their personalities and a sense of freedom did give a lot of impact to some of the ninja affected, Sai probably being the best example right now. It’s like a crude form of Tsukuyomi, where his brother Shin can be blown up again and again in front on him, reforming his body every time due to the Edo Tensei’s binds. Speaking of that, wouldn’t it be more effective for Deidara to just blow himself up over and over using C0, since he’ll just reform anyway?
So it looks like the Edo Tensei does have its flaws after all. We’ve got something that is “binding” each soul to the world they’re in, which is why they keep coming back even though they get killed. If you happen to release whatever that bind is, the soul is released and they are free to go. Being ninja, it’s likely that loads of them have various regrets or things they weren’t able to do in their lives, which provides a way to free their souls if the right ninja fight the right corpses – like Team 10 fighting Asuma, or Neji/Hiashi fighting Hyuuga Hizashi. Granted, if Kabuto removed their personalities like what Orochimaru did with the Hokages he summoned all that time ago, I don’t think the binds of the corpses can go since they can’t think for themselves, which is one way he might counter it.
I remember back in the original series, when Konoha was made to look like the best ninja village ever, that was way more friendly than a village like Kiri who kill classmates for a graduation test. Apparently Konoha isn’t exactly a saint village either, with the secret emotional conditioning methods they use in Root to make ninja more efficient. At least this development on Sai explains his lack of emotion and why he acted like such a dick when he was first introduced, though Danzo making him fight his own “brother” to the death is indeed cruel.
Finally, for someone that was in the Akatsuki, Sasori was reformed by Kankuro really quickly, and surprisingly he didn’t put up much of a fight. Normally people take a beating before their opinions change in a shounen series, but all it took was some words for Sasori to have his soul released. Anything to make the war progress faster I guess.