Prologue: The Newest Sarutobi
Sarutobi Hiruzen was finally in retirement. After almost a lifetime of dutiful service to Konoha, he had passed on the Hokage's hat to a worthy successor. And now he was enjoying a short break at his forest cabin, which was located twenty-five kilometres northwest of the Hidden Leaf.
It was good, Sarutobi thought while chopping some firewood outside his cabin, to finally be free of the burden of leadership. Over the years he had faced many crises and been forced to send friends and loved ones to their deaths. He did not regret his life at all, but he was certainly relieved that those difficult times were behind him at long last. In his twilight years he intended to spend plenty of time with his family and maybe publish a few more books. With Minato at the helm, Konoha was safe and sound and Hiruzen could finally put himself and his family ahead of his duty to others. Just in time, too, since his bones were beginning to ache every morning and evening, and his mind wasn't quite as sharp as he remembered it being when he was younger.
With these idle thoughts circling around in his head, the retired Hokage almost didn't notice a distant whistling sound that filtered down through the canopy of trees above. When he finally did notice it and turned his eyes skyward, he saw through a break in the foliage that in the sky, a spherical object was hurtling like a meteor toward him. Hiruzen quickly leapt into the trees and began to dart through the forest from tree to tree, away from where he predicted the object would crash.
A few seconds later a heavy thud shook the forest trees, startling all manner of woodland creatures, and then a loud boom blasted through the dense flora. A hot wind raked the elderly Sarutobi's back as he continued to move away from the point of impact.
Finally confident that he was at a safe distance, Hiruzen turned around and began to cautiously approach whatever it was that had fallen from the heavens. The closer he got the more certain he became that his cabin must have been absolutely flattened. All around the forest were bright flames, charred earth, and shredded, fallen trees. Dust hung heavy in the air.
Upon reaching the lip of a large crater full of suffocating smoke, the old man shook his head and shed a single tear for his cosy forest abode, which was now nothing more than cindered, shattered charcoal. So much for his short respite from civilisation.
Once the smoke thinned out enough to breathe easily, Hiruzen decided to see if anything was left from whatever it was that crashed on his cabin and ruined his vacation. He jumped into the crater and nimbly climbed down its steep incline. At the very centre of the deep depression he found a smooth, white, spherical… something. It was fairly large and entirely undamaged by its collision with the earth.
"Hrm… curious," the old man whispered to himself, trying to deduce just what it was he was looking at. He'd never seen anything remotely like it before. Perhaps it was some sort of weapon?
Before he could think any further about the nature of the sphere, a loud beeping noise started to come from inside it. A moment later the sphere let out a burst of gaseous steam and began to open. Hiruzen peered inside the orb and tried to make out its interior. Finally, once the door was fully open, he saw that within the sphere was a child – an infant baby boy, to be precise. He lay still on the cushioned seat that comprised the entirety of the capsule's interior.
"A child?" the old Hokage asked himself, bewildered.
As smoke started to creep into the capsule, the child awoke and immediately began to wail loudly. Paternal instincts kicking in, Hiruzen swiftly reached in, picked the small boy up, and pulled him out, gently hushing him. Unfortunately for the old man, the child's wailing only increased in volume as he started to flail about aggressively, thumping Hiruzen with balled fists.
"Umpf! You've got a lot of strength in those little arms, don't you, kid? Ouch." Actually, he thought to himself, That's not normal. No baby is this strong. It feels like I'm getting pummelled by a chūnin!
It was at this moment that the old Sarutobi noticed that something furry was brushing up against him. He looked down and saw what appeared to be a brown monkey's tail. A moment of confusion passed until Hiruzen realised that the tail belonged to the boy, which actually didn't do much to assuage his confusion.
Definitely not normal, then.
He wrapped his hand around the tail in an attempt to lift it up and examine it, but even his light grip on it caused the boy's whole body to freeze up and twitch agitatedly. His loud wailing also trailed off into a pained whine. Hiruzen quickly let go of the tail, which resulted in the boy reacting even more angrily than before, the blows from his pudgy fists hammering down with considerable force.
What a strange child. "Ouch! Stop that!" What should I do with him?
Considering that the boy was all alone, Hiruzen couldn't in good conscience just leave him here to rot. He would have to take him with him back to Konoha. But then what?
"Well, little one, if no one comes to claim you—and somehow I don't think anyone will—then I'll just have to keep you, won't I? Biwako will be delighted, I'm sure. And would you stop hitting me already?"
And so, with the wild little baby boy under his arm, Sarutobi Hiruzen scurried out of the crater and cast a last look at the odd capsule.
I'll ask Minato to send some ANBU to seal this thing for analysis and safekeeping, he decided.
"Well, boy, what should I call you? With your monkey tail you're a good fit for our clan. Hrm, I think you look like a 'Goku'. Sarutobi Goku, what do you think of that, eh?"
Goku answered the old man with a grumpy grunt and a hard kick to the guts, which drove the wind out of Hiruzen's lungs and left him folded over, gasping for breath.
"Well, one thing's certain: you'll be a taijutsu prodigy in no time."