"It's hopeless!"
The Sandaime(3rd) sighed.
At this time, his governing style had softened a lot.
He was old, and his strength had declined significantly.
...
Uchiha Madara stepped onto the land of Hidden Mist.
Beside him was Black Zetsu, with White Zetsu covering his body.
To compensate for his extremely weak taijutsu due to old age, Uchiha Madara chose to wear White Zetsu to avoid any mishaps.
"I didn't expect Hidden Mist to become like this...."
Uchiha Madara smelled a faint scent of blood in the air.
"Lord Madara, the Third Mizukage is a madman; he's almost returned Hidden Mist to the primitive era..."
Black Zetsu spoke hoarsely.
Uchiha Madara nodded.
Even he found Hidden Mist's madness and bloodiness a bit too extreme.....
"But the greenery is quite good...."
Uchiha Madara said casually.
"Everything's ruined, so of course the greenery is good when no one is weeding....."
White Zetsu grumbled.
The three arrived inside Hidden Mist.
(PS: It's still hard to say whether the Third Mizukage was controlled by Madara, because in the original work, the Third Mizukage also led Hidden Mist in the Third Great Ninja War. The original work only explicitly stated that Uchiha Madara controlled the Hidden Mist Anbu.)
Relying on the special abilities of Black Zetsu and White Zetsu,
they easily infiltrated the interior of Hidden Mist.
The Third Mizukage paused, then sharply looked into the depths of the room.
"Who!?"
"Who's there!?"
The Third Mizukage demanded coldly, forming hand signs simultaneously.
A mysterious figure, covered in white swirls, slowly emerged from the darkness.
"Third Mizukage...."
The mysterious white swirl figure's single eye flashed crimson; it was a three-tomoe Sharingan.
(According to the later Edo Tensei, Uchiha Madara could switch between three-tomoe, Mangekyo, and Rinnegan.)
"Uchiha Clan!?"
The Third Mizukage was greatly alarmed.
He instantly recognized the Uchiha's signature eyes!
Immediately following was a powerful mental force, directly invading the Third Mizukage's brain.
The Third Mizukage instinctively closed his eyes.
But the jutsu had already been cast; it couldn't be undone.
The Third Mizukage froze for a moment, then formed a hand sign.
"Genjutsu: Release!"
But the opponent wouldn't wait for him to release the genjutsu.
"Too slow!"
Black Zetsu suddenly appeared behind the Third Mizukage, taking advantage of the instant he was stunned by the genjutsu, attaching to his body and successfully taking control!
"Be my puppet obediently!"
Uchiha Madara walked to the Third Mizukage with a low voice, using his Sharingan to layer on the control again.
....
Two years later, Nagato was three years old.
The three-year-old Nagato had already become the shape Mu wanted.
"Grandpa Mu!"
"Grandpa Hozuki!"
Nagato sat obediently beside Mu.
Mu smiled and waved at Nagato.
"Nagato, you are three years old now, and I want you to complete a mission."
Mu said to Nagato.
Nagato showed reluctance and unwillingness: "I want to stay with my two grandpas; I don't want to leave."
Mu and Hōzuki Gengetsu exchanged glances.
Then he stepped forward and gently patted Nagato's shoulder.
"Once you complete the mission, you can return to your two grandpas."
Mu said patiently.
After some hesitation, Nagato nodded and asked, "How long will that take?"
"Probably several decades..."
Mu's eyes were distant.
"Ah! Several decades? What if Grandpa dies then?"
Nagato's eyes widened as he spoke worriedly.
At Mu's current age, in a few more decades, he would naturally reach the end of his life.
"I will live and wait for your return."
Mu put his hands behind his back.
Nagato nodded, half-understanding: "Then what should I do?"
Mu subtly waved his hand towards the Anbu in the shadows.
"Follow the Anbu!"
Nagato was led away by two Anbu.
Inside the Anbu secret room,
Nagato had a seal placed on him, sealing his memories related to Mu.
It was similar to Sasori's Puppet Manipulation: Concealed Brain Operations jutsu.
(Puppet Manipulation: Concealed Brain Operations: A jutsu that involves inserting extremely small needles through the memory centers of the brain to seal memories. Once the jutsu is released, the needles disappear, and memories return. It allows for safer long-term espionage activities.)
However, Mu wasn't afraid that Nagato would forget him over time.
Because all Mu wanted was for Nagato to evade Uchiha Madara's first layer of detection.
.....
Hidden Rain Village, a red-haired orphan was left on the street.
Nagato slowly opened his eyes.
"Who am I?"
Nagato walked aimlessly, confused, through the streets of Hidden Rain Village.
At the same time, Madara and Black Zetsu were passing through the Land of Rain.
"Lord Madara, another Uzumaki Clan orphan has been found."
White Zetsu immediately sensed Nagato keenly.
Uchiha Madara sighed slightly: "Let's see if he can become a vessel for the Rinnegan."
White Zetsu instantly appeared behind Nagato.
A hand chop knocked Nagato unconscious.
He was brought before Uchiha Madara.
Uchiha Madara first used his Sharingan to read Nagato's past.
He found that Nagato was just an ordinary orphan, with deceased parents and a clean background.
"Let's try the Rinnegan!"
Uchiha Madara directly gouged out Nagato's eyes and implanted the Rinnegan into his eye sockets.
Madara didn't care whether Nagato lived or died.
His understanding of Nagato was...
Sizzle, sizzle, sizzle!!!
When the Rinnegan was placed into Nagato's eye sockets, white mist immediately appeared.
Uchiha Madara was startled! It succeeded!?
He didn't expect that the Uzumaki Clan orphan he picked up by the roadside actually succeeded!
Good, good, good! He searched all over the world and couldn't find one.
Now he found one by the roadside.
Uchiha Madara truly felt like he had been set up.
However, he trusted his Sharingan.
His Sharingan had checked Nagato's background, and there were indeed no problems.
"Since that's the case, then he's the one."
Uchiha Madara immediately selected Nagato, then took Black Zetsu and White Zetsu and vanished underground.
After a long time, Nagato slowly opened his eyes.
He was panting, feeling the power flowing through his eyes.
"I understand why Grandpa Mu chose me....."
The power of the Rinnegan directly broke through Nagato's sealed memories.
....
In the 9th year of the Second Great Ninja War,
Mu celebrated his sixtieth birthday.
At sixty, Mu was still in good spirits.
His legs and feet were nimble; not smoking or drinking had saved Mu from many common elderly ailments like heart or lung disease.
Hōzuki Gengetsu showed obvious signs of aging, with noticeably graying hair.
"Teacher, today is your sixtieth birthday!"
The Sandaime(3rd), Ōnoki, came to celebrate his teacher's birthday.
Mu, as the birthday boy, sat in the middle, only sighing at how time flew by.
Sixty years old, he was already an old man.
Yet, the Second Great Ninja War had not yet ended.
Kakashi and Obito's generation had probably just been born.
As for Naruto's generation, it would probably be another few decades to a dozen years until they were born...
Mu looked at the cake in front of him, then silently made a wish.
"I wish to live!"
As the candles were blown out, cheers and congratulations from everyone resounded.
"May Teacher live forever!"
"May Nidaime(2nd)-sama have a long and prosperous life!"
"May Grandpa Mu live forever, forever and ever!"
Mu closed his eyes, a smile playing on his lips.