"Heck, no."
"Wait, you won't train me?!" Krillin's eyes went wide, "But why not?!"
Korin sighed, closing the lid on the 'Past' pot, which showed an image of the stands at the last World Martial Arts tournament, specifically the area where Tarble and that group had been sitting.
He opened the 'Present' pot, pulling up an image of Tarble, currently training with Lynn, casually flying through the air, SSJP vs. FSSJ. "You want… to surpass this monster?"
"I-I know it's going to be hard, but that's my goal. No matter how long it takes, how hard the road is, I want to have the power to stand shoulder-to-shoulder with the strongest fighters out there. That's my dream." Krillin explained, stuttering a bit.
He had a fair idea of how stupid it sounded. While he didn't know the exact difference, he did know that Kakarot was jokishly strong compared to him, and that these monsters were jokishly stronger than Kakarot… But it was still his dream.
But Korin crushed it with reality. "Look, kid. You need to understand something. I can train you. Make you incomparably stronger than you are right now… but honestly, this is probably your limit." He showed a picture of Kakarot in the jar, "And that's after some insanely intense, long-term training."
"B-but!" Krillin was indignant, but Korin wasn't finished.
"If you train expecting to match a monster like this guy," The image in the jar flipped back to Tarble, "You'll end up getting discouraged, because honestly, even if your drive and talent are greater than any other human out there could possibly match up to, you might learn some tricks that let you match this guy for an exchange or two… When you're his age." The image switched to Roshi for a second, but upon realizing that he was watching weird workout videos just to gawk at the girls in them, the lid went back on the pot.
"So, you're saying that it's pointless. That, because I'm a human, I should just give up…?!" Krillin was crestfallen. He came all this way… only to be told to give up because his goal was impossible.
"I'm telling you to get stronger for yourself. I'm not teaching someone who's going to spend their life slowly losing motivation, kid. I'd rather put you out of your misery now, then let you go through that."
"Wait… So, if I just promise not to compare myself to anyone else…?" Krillin realized.
"Then I'll train you. Can you do that?"
"Understood, Master Cat!" Krillin nodded enthusiastically.
"My name is Korin, brat!" Korin whapped Krillin upside the head with his cane.
And thus, Krillin's long months of training began.
Now, Krillin wasn't actually much weaker than Korin at this point. It took him under a day to figure out that Korin's 'sacred water' was actually just tap water.
But that simply wasn't good enough for the bald-headed warrior. He could immediately tell that there was something beyond just strength that Korin could teach him.
So, Korin gave him a new gi… that weighed over 200 pounds as a unit. Restrained by those, it took the bald-headed human several weeks of concerted effort in order to take the pot once more. During this time, his ability to concentrate during battle, as well as his ability to adapt and predict sudden, unexpected moves during battle, made a qualitative leap.
Krillin wasn't happy with just learning that, though. Over the course of his training, he'd learned something rather interesting about Master Korin.
Master Korin's understanding of 'chi' and 'strength' was second to absolutely none. Even Master Roshi was unable to see what Master Korin could casually comprehend.
For example, Master Korin could precisely say that Krillin's power, when compared to the likes of Tarble, was somewhere between 400,000 and 500,000 times weaker.
By comparison, the current Krillin was only around 150 times weaker than Kakarot.
Master Korin's chi was so perfectly stable and controlled that he could see straight through that sort of thing with incredible pinpoint accuracy. Krillin wanted that.
Six months passed under the tutelage of Master Korin.
Once Krillin's actual strength surpassed Korin's, most of those days ended up being spent in deep meditation. There were entire weeks where Krillin's body didn't actually move a muscle, he was so immersed in taming his spirit and reaching a new level of ki control.
It was difficult to tell whether or not he'd made it, but he knew that he was at least making progress, slowly but surely.
Then, one day, it happened.
Korin got a telepathic call from being known as 'Kami', and immediately went to the 'Earth Observation Pots' as Krillin had begun to call them, flustered from whatever Kami had told him.
Shortly after, the immortal cat woke Krillin from his meditation. "Get up. I found the perfect opportunity for you to test yourself, boy. The Earth needs you, Krillin."
Krillin had but one response. "...Huh?"