King Kai's Planet.
Sitting cross-legged, Son Gohan kept his eyes closed, lost in deep thought.
Since King Kai refused to let him test things out physically, he could only run the numbers in his mind, simulating exactly how far he could push the Kaio-ken.
"From five times… to six times. I can manage sixfold Kaio-ken now. Any higher, and my body will collapse under the strain." His eyes snapped open.
"Six times?! That's insane! Sixfold Kaio-ken means multiplying your base power six times over! Any opponent on your level wouldn't even be able to touch you after that!" King Kai was completely stunned.
He had never expected that a student he had taught so casually would turn out to be such a monster.
Some might wonder, if Gohan could already transform into a Super Saiyan, why bother with a so-called 'outdated' Kaio-ken?
Of course, he had his reasons.
In the original timeline, Gohan underwent Elder Kai's unlocking ritual, awakening a Mystic Form even more outrageous than Super Saiyan 3.
And Elder Kai himself had said it: the Super Saiyan transformation was inherently unnatural, one that damaged the body.
Gohan's Mystic Form, on the other hand, was perfectly suited for him minimal strain, maximum power, and almost no physical burden.
So imagine… Mystic Form stacked with Kaio-ken.
And even if Mystic Form could not be combined with it, what about Super Saiyan God?
That was not mere speculation. After all, Goku had already done it.
As for why a Super Saiyan God could stack Kaio-ken, Gohan had figured it out.
While the manga never explained it outright, Goku's ability to fight Beerus in the vacuum of space strongly suggested that becoming a god fundamentally elevated one's very lifeform.
With that kind of leap in existence, it made sense. Super Saiyan Blue stacked with Kaio-ken was dangerous, yes, but manageable.
After all, Super Saiyan Blue was just the Super Saiyan transformation layered atop the Saiyan God form.
Clearly, that divine boost was no joke.
From a short-term view, Kaio-ken, even tenfold, might seem obsolete and risky. But from a long-term perspective, it was bound to be useful again.
That was exactly why Gohan had sought out King Kai to learn it.
"King Kai, now that I've mastered Kaio-ken, I won't trouble you any longer. Thank you." Gohan bowed politely.
"Wait, wait, Gohan, Kaio-ken is powerful, yes, but I have another move even stronger than that. Don't you want to learn it?" King Kai's eyes lit up.
After all, it was not every day a genius walked into his lap. No way was he letting Gohan leave so easily.
"No thanks. I'm not interested." Of course Gohan knew exactly what King Kai was talking about.
The Spirit Bomb.
Yes, that very same 'raise your hands, get beaten senseless, then throw it' move.
"Why not? My Spirit Bomb is practically unbeatable! As long as the target has evil in their heart, it can wipe them out! You're young and pure at heart, you'd definitely master it!" King Kai looked genuinely puzzled.
"I can't say why, but I'm certain I won't be able to use it." Gohan's tone was firm.
"No, no, since you've learned Kaio-ken, you have to learn the Spirit Bomb too!" King Kai stood his ground.
"Fine, fine… I'll try," Gohan said helplessly. Then he added with a smirk, "Forgive me for asking, but… King Kai, can you actually use this move?"
"Ahem, of course I can! Enough talk, focus your mind!" King Kai's cough did little to hide his awkwardness.
…
A full day later.
"Why don't we just forget it, King Kai? My stomach's growling here." Gohan gave up.
"Why… why can't even a two-year-old gather the energy of nature?!" King Kai was beside himself.
Of course not. While Gohan was not exactly evil, in his past life he had definitely had a fair share of… ahem, less-than-pure habits.
Especially with those few terabytes of 'study material' forever etched into his mind.
The Spirit Bomb required pure, pristine energy from all living things.
"Ahem… let's not dwell on the reason. How about this, I'll introduce you to someone who's guaranteed to learn it," Gohan offered.
"Deal!" King Kai's greatest wish was to show off his Spirit Bomb and Kaio-ken to the other Kais.
And Gohan's candidate? Son Goku himself. Only someone as ridiculously pure as Goku could master it.
Even after having a kid with Chi-Chi, the man's heart was utterly free of impure thoughts.
"King Kai, I won't bother you any further."
"Stay for a meal first?"
"Sure."
… Half an hour later.
King Kai's eyes were bulging.
The table before Gohan was buried under stacks of empty bowls and scattered bones.
Even Bubbles the monkey would have turned away crying.
"You… you just ate a month's worth of my food in one sitting!" King Kai could hardly believe the small figure barely four feet tall had put away that much.
"Thff wazz relly good!" Gohan mumbled through a stuffed mouth.
"Swallow before you talk!" King Kai barked.
Gulp. "Ah, that hit the spot! I've always had a big appetite."
"Big appetite my! Fine, fine, eat all you want, just don't burst!" King Kai rolled his eyes.
"By the way, King Kai, keep an ear out for me. Sooner or later, the Grand Elder of Namek will contact you asking to find me. When that happens, let me know immediately."
"Oh? Namek? I didn't think you'd been there. As far as I know, Earth doesn't have the tech for interstellar travel, let alone a ship that could reach Namek."
"Don't overthink it. You know how I got here, and you know about the Dragon Balls. That's all you need to know." Gohan waved it off. He wasn't in the mood to explain.
"Fair enough. I'll let you know when he calls."
"Good. I'll bring the person who can learn the Spirit Bomb to you later. Teach him well."
"No problem, but are you sure he can do it?"
"Absolutely. He'll blow your mind."
"Then I'll be waiting."
…
With a whoosh, Gohan vanished.
Earth.
Right now, Son Goku was in the Arctic tundra, trading blows with Piccolo.
"Huff… what's wrong, Goku? Out of steam?" Piccolo panted heavily.
Goku was on his hands and knees, barely able to stand.
"Pi… Piccolo… I can still fight!" He staggered upright, legs trembling.
Piccolo, too, was only barely on his feet.
"Yo… Dad, Piccolo, you two look like you're having fun," Gohan's voice rang out.
Thud!
Piccolo collapsed on the spot. Goku followed right after.