Even if Orochimaru were to collect enough Sharingan genes and successfully fuse the Mangekyō Sharingan with his body, he wouldn't necessarily lose his mind. However, there would certainly be mental side effects. The intense spiritual power required to wield the Mangekyō would undoubtedly affect his psyche.
When using the advanced abilities of the Mangekyō Sharingan, the body is put under incredible strain. Over time, side effects such as myopia, eye bleeding, and severe physical pain are almost guaranteed. The sheer power of the ocular jutsu overloads the body's capacity to manage the strain, leading to these complications.
Some might wonder: If a body is strong enough, does that mean using the Mangekyō Sharingan would have no side effects?
The answer is yes with a strong enough body, the side effects can be minimized or even eliminated.
Take Uchiha Obito, for example. After transplanting the cells of the First Hokage, and later integrating White Zetsu's body, he was able to use his Mangekyō Sharingan freely, without suffering from common side effects. He didn't experience bleeding eyes, myopia, or body pain, despite constantly using powerful techniques like Kamui.
Orochimaru hypothesized that after using an advanced genetic enhancement serum, he, too, would be able to use the **Mangekyō Sharingan without those physical side effects. Moreover, if he managed to fuse the cells of the First Hokage into his body, it would even be possible for him to use the Rinnegan without difficulty.
To Orochimaru, the Rinnegan was far more advanced than the Mangekyō Sharingan at least a full level above it in terms of power and capability.
Obito, despite having the First Hokage's cells, struggled when it came to the Rinnegan. It was clear that simply integrating Hashirama's cells wasn't enough to fully master it. Even with the strength of those cells, the Rinnegan was too much for his body to handle comfortably.
Using a pair of Rinnegan? That was an entirely different challenge. To control both eyes of the Rinnegan, a ninja would need the physique of someone from the Uzumaki or Senju clans those with an exceptionally strong life force and chakra reserves. Just transplanting Hashirama's cells wasn't enough.
But then, there was Uchiha Madara. He didn't have the natural physique of an Uzumaki or a Senju, yet he could wield both Rinnegan eyes without difficulty. Why? Because he was the reincarnation of Indra, possessing the chakra of Hagoromo's eldest son. Madara's lineage gave him direct access to the power of the Sage of Six Paths, making his situation unique.
---
Orochimaru pondered over these things. "I'll only know for sure once I obtain and experiment with the First Hokage's cells," he thought. Hashirama's DNA was the key to unlocking the true potential of the Mangekyō and, eventually, the Rinnegan.
Satisfied with his conclusions, Orochimaru stopped thinking about it for the time being. He closed his eyes and quickly fell into a deep sleep.
---
The First Shinobi World War officially ended following the deaths of the Second Hokage and the Second Raikage. Their sacrifices led to the rise of Hiruzen Sarutobi as the Third Hokage, marking the end of the conflict.
Since the coup that killed the Second Hokage was instigated by Kinkaku and Ginkaku, two rogue shinobi, it was deemed unrelated to the Land of Lightning. As such, the peace-loving Konoha didn't pursue further retaliation.
With Hiruzen now in power and Danzo establishing his secretive organization, Root, Konoha entered a period of formal development and recovery.
---
Year 20 of Konoha's Calendar
Four months had passed since Orochimaru moved into his new home. In total, it had been three years since Orochimaru arrived in this world. Another beautiful, colorful morning broke over Konoha Village. The sunlight crept through the curtains, gently waking the village to a fresh new day.
In the Hokage's Office, the Third Hokage sat at his desk, hands resting on his chin as he looked thoughtfully at the three young shinobi standing before him Orochimaru, Tsunade, and Jiraiya.
As their teacher, Hiruzen felt a deep responsibility to guide them, but now that he was Hokage, he had other duties that kept him from teaching them as closely as he once had. He could no longer run around with his students, personally completing missions and offering on-the-job instruction.
Still, Hiruzen made sure his students had access to resources that most civilian ninjas did not, ensuring they were equipped for success. But accompanying them on missions? That was no longer possible. After all, it wasn't as if the Hokage could just run around with his students in peacetime.
Today, however, Hiruzen had called the three of them to discuss their future missions.
Among the three, Jiraiya was a bit careless and prone to outrageous behavior. Tsunade had a fiery temper and could easily lose control in unexpected situations. Only Orochimaru was consistently calm and collected.
As Hiruzen thought about these things, he finally spoke. "Orochimaru, from today onward, you will be the captain of this team."
"What?"
Tsunade was taken aback, but it was Jiraiya who exclaimed in disbelief.
"Why?" Jiraiya demanded. "Why is Orochimaru the captain? I can do it too! I mean, look at me Jiraiya-sama is handsome, skilled, and more than qualified to lead this team!"
Hiruzen smiled slightly but said nothing. Tsunade, however, scoffed and rolled her eyes.
"Jiraiya, do you even know your own abilities?" Tsunade shot back, not holding back her criticism. "What do you have over Orochimaru? Is it your strength? Your resilience? Your judgment? Oh, wait… maybe it's your perversion that's superior!"
"Tsunade, that's not fair!" Jiraiya protested angrily. "Don't look down on me!"
"Isn't it true, though?" Tsunade teased, giving him a sly smile. "Big pervert…"
The two were moments away from bickering again when Hiruzen raised his hand to silence them. "Enough. Among the three of you, Orochimaru is the most suitable to be the captain. From today forward, he will lead your missions."
Knock knock knock!
Before Hiruzen could finish, someone knocked on the office door.
"Come in," he said.
The door opened, and a middle-aged man wearing glasses and a white coat rushed in, visibly excited.
"Hokage-sama! The experiment was successful! The experiment was successful!" the man exclaimed, his voice full of enthusiasm. However, as soon as he spotted Orochimaru, he paused, his excitement briefly fading.
"Ah, teacher, you're here too?"
"Teacher?" Tsunade and Jiraiya blinked in confusion, staring at the man.
Did he just call Orochimaru… teacher?
This was… unexpected. What was going on?
Orochimaru remained calm, unfazed by the strange looks. "Don't mind me. Continue with your report."
"Yes, of course teacher!" The man in the white coat nodded and turned back to Hiruzen. "Hokage-sama, the recovery potion experiment… it was a success!"
"Success?" Hiruzen's eyes sharpened with interest. "Explain in detail."
"Yes, Hokage-sama! Based on the research given by Orochimaru-sensei, I began developing the recovery potion three months ago. I'm happy to report that we have finally achieved a breakthrough…"