Shisui felt his Kotoamatsukami was insidious enough, but after hearing about Edo Tensei, he realized that the Second Hokage, Tobirama, was the most insidious of all.
Shisui's Kotoamatsukami at least had a side effect; once used, it had a cooldown period of ten years.
But what about Edo Tensei?
What side effects did it have?
The only drawback was that it cost a life, requiring a Shinobi with chakra as a sacrifice to summon the soul of the deceased from the Pure Land.
But for the powerful who viewed human life as mere grass, this was not a drawback at all.
Furthermore, the resulting Edo Tensei body was immortal; any damage from being shattered or severed would regenerate rapidly.
Because they cannot die, they won't die even if their chakra is exhausted; instead, their chakra will simply recover again.
In theory, they possessed an inexhaustible supply of chakra.
Shisui looked at the Third Hokage with his hollow eyes: "Hokage-sama, such a technique is truly too taboo."
The Third Hokage nodded: "That is why it is a Forbidden Jutsu. Moreover, such a technique is not something an ordinary person can learn."
The Third Hokage turned to look at Danzo: "Danzo, the best way to deal with Uchiha Madara is with an Edo Tensei body."
Danzo nodded: "An Edo Tensei body can only be sealed. Uchiha Madara is not skilled in sealing; his Chibaku Tensei merely uses rocks to restrict the enemy, which is not an orthodox Sealing Jutsu."
Madara's mechanics were unsolvable; Limbo could only be perceived by the Rinnegan and Six Paths Sage Mode.
The Shinobi Allied Forces simply didn't have anyone like that.
Since Madara's mechanics were unsolvable, they would use an unsolvable technique to deal with Madara.
Edo Tensei, because it was unsolvable, could only be sealed.
This was the best way to deal with Madara. They only had one life; they couldn't possibly use their flesh and blood bodies to fight to the death against Madara.
The margin for error with flesh and blood was too low. Because Edo Tensei provided an immortal body, the margin for error was very high, making it the best weapon to counter Madara.
Shisui then said: "The intelligence provided by Ryou-senpai mentioned that Uchiha Madara has a type of chakra-conducting black rod. That thing can restrict the flow of chakra within a Shinobi's body."
Jiraiya also remembered: "Old Man, Fukasaku-sama and Shima-sama also suffered from Madara's chakra rods."
"When they were struck by Madara's black rods back then, even their Senjutsu was blocked. I suspect those black rods will seal the chakra of an Edo Tensei."
The Third Hokage stroked his chin: "We just need to be careful when the time comes."
"In the end, we are only using Edo Tensei to restrain Madara. What will truly deal with Madara is Sealing Jutsu."
Madara's mechanics were just like an Edo Tensei body—so strong that one wouldn't know how to kill him.
In such a case, the only option is to try every possible way to seal him.
The Third Hokage clenched his fist, having already made a choice in his heart.
Minato looked at the Third Hokage with some pity. A while ago, the Third Hokage had come to his house to take the Uzumaki Clan's sealing scroll and learned a Sealing Jutsu.
The Third Hokage didn't let Kushina or Minato see him while he was learning it.
But they had both guessed it: it was the Reaper Death Seal, which could summon the Shinigami.
At the cost of one's own soul, it summons the Shinigami to devour the target's soul and seal it permanently. However, after the Shinigami devours the target's soul, one's own soul will also be devoured by the Shinigami.
Afterward, the souls of oneself and the enemy will hate and struggle against each other inside the Shinigami's stomach, never to be reincarnated for all eternity.
This was an evil technique that sacrificed oneself, as well as one's peace after death.
They had talked for so long, but none among them could learn Edo Tensei.
The Third Hokage asked: "Where is Orochimaru?"
At this point, Danzo could no longer keep things hidden. While they were guarding against each other—the Shinobi World had already gone to the dogs!
Danzo said: "Orochimaru is not in Konoha; he took his two disciples to Ryūchi Cave."
"Ryūchi Cave?!"
Jiraiya was pleasantly surprised that Orochimaru was still alive, but at the same time, he wondered what Orochimaru was doing at Ryūchi Cave.
Was he planning to hide in Ryūchi Cave to escape Madara's Infinite Tsukuyomi?
Based on Jiraiya's understanding of Orochimaru, he really would find a hole to crawl into for a lifetime just to stay alive.
Danzo said: "Orochimaru transplanted White Zetsu cells, and his body has been enhanced. He plans to learn Senjutsu to strengthen the Edo Tensei bodies of Lord First and Lord Second."
Edo Tensei has one flaw: the power of the Edo Tensei body cannot reach the peak strength the deceased had while alive.
It can only approach it, not surpass it.
However, with an inexhaustible supply of chakra and an immortal body, it sacrifices explosive power for increased endurance.
Orochimaru had only just mastered Edo Tensei. He needed to use Senjutsu to strengthen Edo Tensei and enhance his own Shinobi stats to summon more Edo Tensei bodies.
When the time comes, with thousands of zombies besieging Madara, even if Madara were made of iron, he would be worn down to death.
The Third Hokage frowned. Learning Senjutsu was very dangerous, and the Senjutsu of the Three Great Sage Regions was all the same in that regard.
It was very difficult to perfectly balance the natural energy, physical energy, and spiritual energy within the body.
If one were not careful and absorbed too much natural energy, it would lead to the body's collapse.
It was precisely because learning Senjutsu was so difficult that so few people in the Shinobi World mastered Sage Mode.
Even a genius like the Second Hokage, Tobirama, could not learn the Shikkotsu Forest Senjutsu passed down by the Senju Clan.
For Orochimaru to go and learn the Ryūchi Cave Senjutsu, the most dangerous of the Three Great Sage Regions, was a bit of a gamble.
The Third Hokage said to Danzo: "Can you call Orochimaru back? We can't afford to take risks at a time like this!"
Danzo shook his head: "Orochimaru is your disciple; you know his personality. For a person like him, the more difficult a technique is, the more interested he is in learning it."
"Even if he can't learn it, he will find a way to create a derivative technique from it."
Listening to Danzo's words, Jiraiya thought of the Cursed Seal Orochimaru had shown when the Sannin faced off against Madara.
Fukasaku-sama had said it was a simplified form of Senjutsu.
Orochimaru was that kind of person, possessing an insatiable hunger for Ninjutsu that would never be satisfied.
He was like a little gluttonous snake that could never fill its belly, and one day, he might devour the entire Shinobi World.
Jiraiya rubbed his head. If they really had a chance to defeat Madara and Ryou, Orochimaru might become a new trouble for the Shinobi World.
This was also why the Shinobi World fell into endless wars—because there were simply too many god-like people.
The Third Hokage wanted to talk to Orochimaru about Madara now, but Orochimaru was not present.
He then said to Danzo: "Danzo, send the intelligence on Uchiha Madara to Orochimaru. He should have left some contact tokens of his own in Konoha."
Danzo nodded: "Yes, Orochimaru is still closely following the matter of Uchiha Madara."
The Third Hokage said: "Regardless of whether Orochimaru has mastered Senjutsu or not, he must return to participate in the battle before the Shinobi Allied Forces attacks Amegakure."
Danzo nodded again: "I will tell him."