The Reanimation Jutsu meant that the deceased could be summoned back to the physical world through specific means. The contract scroll for Ryuchi Cave meant the opportunity to learn Sage Mode from the White Snake Sage. These were the two things Allen desired most, and things he absolutely had to obtain.
The former was particularly critical. Although the Scroll of Seals recorded the methods for its study and cultivation, the text was laden with terminology that only a native of this world could truly grasp. Allen couldn't make heads or tails of the extensive descriptions regarding the Pure Land.
This was why, in the end, only Orochimaru and his subordinate Kabuto mastered the Reanimation Jutsu. In the entire world of shinobi, only Orochimaru was so obsessed with breaking the boundary between life and death that he had undoubtedly conducted exhaustive secret investigations into the Reaper and the Pure Land. Through that process, he came to understand the nature of the afterlife and the fundamental mechanics required for the Reanimation Jutsu to succeed, eventually bringing the Second Hokage's invention back into the world.
For Allen, the combat strength of the reanimated powerhouses was secondary; the knowledge and ninjutsu they possessed were the true treasures.
Driven by his own hunger for the unknown power of Nen, Orochimaru, though slightly reluctant, ultimately agreed to the trade. After receiving the advanced applications, affinity testing, and development techniques for Nen, he promptly handed over the Ryuchi Cave contract scroll and the specific instructions for performing the Reanimation Jutsu.
As for the underlying theory... Allen had zero interest. He didn't care to know the secrets of the afterlife; he only needed to know how to summon the dead.
In the days that followed, the two coexisted peacefully, each occupied with their own affairs. This unspoken accord lasted for about a month, until a secret message from Root broke the silence.
"Hehe, what does Danzo want from you now?" Orochimaru asked with a hint of mockery. He was dying to know how Danzo would react if he ever found out that one of his most trusted subordinates had long since defected and entered a partnership with his rival.
Allen tossed the two letters onto the table and replied with a light chuckle, "Nothing unexpected. Kakashi has led the newly formed Team 7 out of the village for a mission in the Land of Waves. This Genin squad contains both the last survivor of the Uchiha, Sasuke, and the Nine-Tails' Jinchuriki, Naruto Uzumaki. His orders are for me to find an opportunity to assassinate Sasuke and frame you or someone else for it, while simultaneously ensuring the safety of the village's 'war machine.' Since the Land of Sound is relatively close to the Land of Waves, and my recent reports suggest you've been quiet, I'm the natural choice for the job."
"Oh? Placing the Jinchuriki and the Uchiha orphan in the same squad... is the old man Hiruzen playing that tedious 'bonds' game again?" Orochimaru's lips curled into a smirk.
Allen nodded slightly. "Indeed. He's always done that, using the most fragile human emotions as a form of kidnapping, binding the destinies of two or three people together so they can't easily escape the village's grasp. I have to admit, it's quite a despicable tactic. Unfortunately, it doesn't work on everyone. The old man fails to realize that relying on emotion to maintain loyalty to an organization is the most unreliable method. Only interests, and interests alone, can truly unite people in the same camp."
"Quite right. Common interest is the prerequisite for cooperation, just like us. But... do you truly intend to kill Sasuke Uchiha?" Orochimaru probed cautiously.
"No, of course not. I know he's your prey. But regardless, I'm still Danzo's subordinate in name, so I have to put on a bit of a show," Allen remarked nonchalantly.
"And how do you plan to do that? Putting on a performance in front of Kakashi is no easy feat." Orochimaru's expression relaxed considerably upon hearing that Sasuke wasn't actually on the chopping block. Otherwise, he couldn't guarantee he'd be able to protect his precious, rare vessel.
"It doesn't matter. I don't plan on returning to Konoha until your plan is set in motion anyway. Whatever the higher-ups think is irrelevant; I just need to maintain the illusion of absolute obedience to Danzo's orders."
With that, Allen stood up, stretched his limbs, and headed to the adjacent training field. He waved over Karin, who was in the middle of a combat drill. She stopped immediately and ran over. "Allen-sama, do you have orders?"
"Pack your things. We leave for the Land of Waves in ten minutes," Allen replied directly.
"Understood!"
Karin nodded vigorously and hurried back to her temporary quarters. She quickly wiped the sweat from her face and body, donned the suit of leather armor that significantly boosted her strength, reflexes, and stamina, and threw a purple coat over it.
Looking at her developing reflection in the mirror, she adjusted her glasses and whispered to herself, "Go for it, Karin! Seize this rare chance to be alone with him! You can do this!"
With that, the red-haired, slightly eccentric girl rushed to the village entrance to begin the journey to the Land of Waves with Allen.
Watching their figures disappear into the distance, Kimimaro finally couldn't help but ask, "Orochimaru-sama, is it really alright to cooperate with that man? I feel he is simply using us."
"Hahahaha! It's perfectly fine! I know he is using me, but I am using him just as much. Especially this power called Nen, it allows me to take a massive step toward immortality," Orochimaru explained with a laugh.
To him, being used was irrelevant; what mattered was getting what he wanted. If he weren't willing to be used, he would never have collaborated with someone like Danzo in the first place.
"Is this 'Nen' truly that miraculous? Can it even cure my illness?" Kimimaro asked, his voice laced with doubt.
"Certainly! As Allen said, Nen is a power of infinite possibilities, a reflection of one's true heart. The more you desire something, the more that desire manifests as a Nen ability. I believe it can cure you. Come, let us return to the laboratory to continue the modifications on your body. Housing both Chakra and Nen simultaneously is no simple task, even Karin, with her Uzumaki bloodline, had to put in a great deal of effort."
Orochimaru led Kimimaro back into the depths of the Sound Village's sprawling underground tunnels. With the successful experiment on Karin as a precedent, he was eager to validate his findings on a second subject. Kimimaro, possessing a powerful Kekkei Genkai but plagued by a terminal illness, was the perfect candidate. After all, a bloodline disease was beyond the reach of medical ninjutsu; rather than waiting for death, it was better to try an entirely different power system.