Back in the capsule corp labs, Bulma and Yamcha sat across from each other. Puar had settled into a nap before Goku left, so only the two were left to talk. Yamcha was just launching into his crash course in Ki and the Yin and Yang split.
"So this Ki energy that you and the others use is split between Yin and Yang?" She questioned.
"Correct. Everything has ki, it is the energy that all living things produce. The split comes from the metaphysical separation of body and mind. Because the mind is linked to the soul to give it form, both mental and spiritual abilities come from Yin energy."
Bulma nodded, starting to get a grasp on how this mysterious energy worked.
As she was thinking, a blue glow fell over her, looking up she noticed Yamcha holding a glowing blue sphere.
"Think of it like this," he started, holding his palm out and letting Bulma feel the warmth of the energy held there. "This is physical energy. The higher someone's Yang energy is, the more of this they can produce. However, with the application of Yin, or mental/spiritual energy, "
Bulma watched as the inside of the sphere began to rotate rapidly amd shrink in size.
"You can change the shape and form of the energy. With incredibly high levels of yin energy techniques bordering on the magical can be created. Think about the sealing ability Tien and Roshi attempted on Piccolo. With their control they were able to target the enemy's energy signature, compress it, and seal it into a vessel."
"Incredible." Bulma looked on in awe. She never thought that the crazy abilities her martial artist friends had would be almost scientific at its root.
"So stuff like the energy blasts Goku uses are internal physical energies projected outward, with the mental energies acting as a containment field to give the projection form?"
"Correct!" Yamcha praised, "You pick up on this fast, not that I'm too surprised."
"So," she started, pushing through the smug satisfaction she felt. "Now that I've got some context to what you were talking about, let's talk about your results."
Pulling out a folder with several sheets of paper in it she continued, "You're muscle fiber, skeletal structure, and organs structures all seem to be denser than a normal human's. Not on Goku's level, but a definite change. The biggest change however, is in the eyes and brain." She pulled out three sheets, one containing a baseline human's readings, one his, and one Goku's. The results she described showing clear as day.
"The optic nerve has developed new pathways and seems to have become denser and more durable. In response, the occipital lobe shows increased activity, but is not showing any signs of overwork or damage. I'm guessing this would be because of ki?" She slid another paper detailing the normal optic and brain activity, and contrasting it with his own.
"Yes," Yamcha responded, eyes flicking rapidly over the results he was given. "Ki can nourish and improve organs, making them perform at higher levels."
Bulma nodded, having guessed as much from learning about saiyan physiology and some of the metaphysics of Ki.
"The only thing that stands out as dangerous is the DNA related to your eyes." She added, a trace of worry entering her tone. "The genome seems almost malleable, meaning that it is susceptible to mutation."
Surprisingly, the man across from her only nodded while skimming the paperwork she had given him.
"You knew?" She questioned.
"I suspected," came the answer. "In the memories there were eye abilities, dojutsu as they called them, that could evolve. I think with the right stimulation they can change."
"Well be careful, Yamcha. Evolution doesn't mean perfection. There have been plenty of species that evolved new traits only to die out because of it."
Thinking of the rapid degradation of the mangekyo sharingan, he nodded. He would have to be careful. He was unwilling to lose his sight, and he didn't want to lean too heavily on the dragon balls for his problems.
"I will, I promise. The last thing I want is to lose my eyesight, or worse." He smirked at this and put on an over the top, swooning voice.
"How would I bask in Bulma-swann's beauty if I lost my ability to see."
He yelped as a blushing Bulma smashed the top of his head with her fist.
"TAKE THIS SERIOUSLY YOU IDIOT."
An hour later they finished all the serious talks. "It's getting late," she offered "we have plenty of rooms if you want to stay here for the night."
"Thanks," he replied, seemingly un-bothered by the multiple bumps he'd earned over the hour with his occasional teasing. "I think I'll take you up on that. Tomorrow I'm heading to Korrin's tower. I've got some ideas I need help with, and who better than the guardian of earth right?"
"I guess," she answered. She had a ki cram session earlier, but she was far from being proficient. "Let's go then, I'll bring you to a guest room."
The night passed and with a brief goodbye, and a promise to not disappear, Yamcha departed. He left Puar at Capsule Corp for now, the high altitudes of Korrin's tower wouldn't be good for him.
He didn't bother with Upa and Bora at the base of the tower, though he did get a chuckle out of remembering Krillin's brief crush on the young Upa.
Using the lessons from his memories of being a ninja, he set off in a sprint up the side of the tower.
After a full day of running, a breathless and sweat soaked Yamcha made it. Panting and drenched, he flopped bonelessly to the floor.
"Sweet Kami, that was brutal. Goku did this at 12?"
"Yeah, that Goku is one of a kind huh?"
Yamcha jumped, or he tried to. In his current state he kind of flopped like a fish out of water.
He managed to crane his neck up to meet the gaze of a bipedal cat with a staff. He relaxed a bit.
"Master Korin I presume?"
"Yeah that'd be me, here eat this." Korin said while throwing a small bean to Yamcha.
"Senzu bean?" He thought while crunching into the bean. "I have to see if I can get a small stock of these before Yajirobe eats all of them" he scowled internally at the thought as his body returned to full strength. Mystical artifacts capable of healing any injury, all wasted on a glutton with more appetite than sense.
"Thank you master Korrin, I came for training, and three requests."
"Oh?" The cat's whiskers twitched, "training is all good, but I'm not sure how much good it'll do you at your level. As for the other requests, I make no promises. What are they?"
Yamcha bowed at a 90 degree angle.
"Thank you, Master Korin. First request, I would like permission to go and train under Kami." He began listing his requests.
"Shouldn't be an issue, between what I can sense in your heart and your current power, you should be a good candidate."
Yamcha nodded, "Second request, can I have a bag of senzu for emergencies? You know how often Goku and everyone else gets into life or death battles. It would be good to have back up in case of emergencies." Before Korin could respond Yamcha continued
"And third, Goku's heart is damaged, we think it's left over poison from the ultra divine water. Can I have a small sample so we can try and make an antidote?"
Korin sucked in a breath. "Damn, I knew the kid was too young for it, but there wasn't much of a choice at the time."
As he was about to respond, Yamcha continued once again.
"If you agree, I can offer monthly deliveries of super high quality seafood sealed in capsules so they won't expire!"
The sound of dripping water could be heard on Korin's tower. Looking up from his bow, Yamcha saw Korin drooling. Behind Korin he saw Yajirobe peaking his head around the corner, drooling just as much.
"DEAL!" They both shouted in unison, an almost overflowing bag of 50 senzu swiftly flying towards his head. He dug out his capsule case and put the bag in an empty one.
"Wow," he thought to himself "That was easier than I thought it would be".