When tail beasts (bijū) are extracted from their Jinchuuriki, the Jinchuuriki dies.
All seven Jinchuuriki died after the Akatsuki extracted the bijū from them. Gaara was resurrected by Chiyo using the "One's own life reincarnation" jutsu.
So why do Jinchuuriki die when bijū are extracted?
What are the reasons behind the death of Jinchuuriki after the extraction of bijū?
The reason are not been clear, probably it never will be, now that Naruto is scheduled to end this year.
The Sage of Six Paths told himself that no matter what, if a Tailed Beast is extracted from someone, they die.
I believe that's canon material and a fact in Narutoverse. I guess we just have to make our peace with it.
On a personal note, in my opinion, when someone becomes a Jinchuuriki, the huge chakra of the Tailed Beast enters into the ninja's body and gets mixed up with that of the ninja's.
Imagine the body of ninja is water, and the ninja's chakra is a pinch of sugar dissolved in the water. The process of turning into a Jinchuuriki would be like adding salt (= Tailed Beast's chakra) to the mixture. Now to extract the Tailed Beast's chakra, it's impossible to do so without drying up the ninja first, i.e. Ninja has to die.
After some searches, discussion on forums and answers posted here, I came up with the following conclusion, which is based on the content of the manga up to chapter 692 and contains spoiler.
Let's start with the term Jinchūriki. The term Jinchūriki (人柱力 (Hitobashira-ryoku); Literally meaning "Power of Human Sacrifice") implies that human is sacrificed when Biju is implanted or sealed inside. In other words, when a human become Jinchūriki, their body is sacrificed for Biju.
Biju, also known as Chakra Monsters, is a living form of chakra. That huge amount of chakra is sealed, but can be used with high level of training like how Killer B (Hachibi) does. Biju acts as a part of the body or the body's chakra and when all chakra is lost the person die, so healing and restoring chakra should keep Jinchūriki alive. However, the case is different when Biju is extracted: the essential part to live, the life force, is also lost. To add to the argument, this question describes that life force is essential to be alive and why Juubi's Jinchūriki does not die after extraction of Biju. Resurrection of Gaara after extraction of Shukaku by Chiyo using the "One's own life reincarnation" jutsu shows that the life force is essential to keep alive.
Even Hagoromo said," Madara was once a Jinchūriki. So now that he no longer has a Biju in him, there is no saving him".
Death of Jinchūriki after extraction of Biju is inevitable, unless there is way to provide life force as mentioned above or other ways. If there was any safe Biju extraction method, then why elite shinobi from different village, Uzumaki clan, Third Hokage who knew almost all jutsu of Konoha, did not know such type of jutsu or tried to invent it? There are lots of forbidden Jutsu which are powerful and extraordinary. How can be this possible that no one was able invent it? Uzumaki clan also die, but they resist and can live longer than other Jinchūriki .
Naruto was at the stage of death and was saved after putting Kyuubi. Otherwise, death of Naruto was inevitable.
The Jinchuuriki doesn't necessarily die when their Biju are extracted.
The Jinchuruuki can survive the extraction of Biju in the following cases:
- The Jinchuuriki has enough life force (like the Uzumaki clan - being Ten Tails Jinchuuriki gives enough life force for the host)
- The Jinchuuriki receives immediate medical attention
- Safe Biju extracting method is used
The main reason for the death of a Jinchuuriki is due to the weakened state of the host body, and the host's strong dependence on the Biju chakra for its survival. Such cases are:
- Moving the Biju to the next host when current host is about to die - they are weakened already
- When the Biju is forcibly extracted by others. In such case, the Jinchuuriki will be forced (beaten to near death by Akatsuki members) for the extraction process
We haven't seen any other case where the extraction of a Tailed Beast caused death to their host, yet.
There are a couple explanations. 1) Jinchurikki are sacrifices to contain (and control) Bijuu. It seems they latch themselves on to the Jinchurikki's life force. We have to understand that there were no Bijuu Beasts to begin with. They were Juubi's chakra. Hogoromo made them into nine different entities, by expending his own life force.
It's entirely possible that the Bijuu substitutes as the life force of the Jinchurikki once they are sealed inside someone. The resiliant Uzumaki or Senju relatives can not die instantly, but they are going to die anyway.
Chakra is something that mixes with life force and as explained in Naruto, if you exhaust your chakra, you die. Bijuu extraction methods does not differentiate between a Bijuu's chakra and a persons own. It depletes all of it in one go. And since Bijuu is basically chakra, the extraction casuses fatality to the host.
Bee was able to stay alive after extraction via connecting to a bit of Gyuki's tail containing its chakra. Naruto got Kurama's chakra else he also would've died.
think of a human body as a chakra container. when you put a biju inside the body needs to slowly grow to store all of that massive amount of chakra. if I'm not mistaken inserting a biju can kill the host (since his body can't adapt fast enough to the extra chakra) and that was one of the reasons minato and kushina didn't put the entire kyubi inside naruto.
now, when the biju is removed the body also needs to adapt to the loss of chakra.
let me put it in this way. when you were born your chakra was a glass of water. when you fused with the biju you slowly became a balloon. it was painful and you could have pop but you managed. now they took away 99% of what you were. how would look the balloon? nearly completely depleted. now remember you got a beating and are already using a sizeable amount of chakra to stay alive and slowly heal. when you had the biju chakra that was easy but now... depending on how hard was the beating your body won't be able to heal fast enough and will completely deplete itself. congratulations. you died.
Uzumaki clan has an unusually large amount of chakra so the difference between having or not having the biju chakra isn't as large as with other clans. it's still massive but they have it easier so they survive longer. also naruto didn't have a full kyubi so the difference was even less (still massive but every bit counts) and he got the other half kyubi from his father. that's why he survived even when they removed the half kurama he had.
there's an extra piece of info. when forcibly extracted you don't just remove the biju chakra but also possibly a good amount of chakra from the host as they are mixed and the process ensures all the biju chakra is removed. this means the jinchuriki loses not only the biju chakra (which is probably over 99% of the total) but also a good amount of his own human chakra. if using a more natural method of splitting the two and the consent of the biju and the human I do believe it's possible to ensure the jinchuriki would survive extraction but it's not an easy task since whoever would perform the removal would want to contain the biju in some way and the biju won't agree to such a thing unless extremely rare circumstances. I suppose naruto could pass part of kurama to boruto to save his life but I don't bet anything on it.
