{6 months later}
The sounds of raging winds filled the air as the two silhouettes threw fists at each other. Both Gokus were exchanging punches and kicks but every movement had a certain level of elegance to it. Their natural movements made the fight much nicer to look at but each Goku knew that getting hit by any of the moves of this martial art will hurt very much as they experienced it through their bodies by experimentation and training.
That in itself was a great achievement as it made Goku discover the unique ability of his Saiyan physique. It is hard to describe as he was not completely sure of what it does but from what he can analyze, it was a genetical trait that allows him to become something like a sponge and have an insane version of the muscle recovery ability that all humans have but on a greater scale.
What happened was that when the Goku clones were fighting each other, one of the clones got harmed quite badly but after a few hours, the harmed clone not only healed but became stronger physically and his Ki level rose. This method, however, was a bit dangerous as the more damage his body accumulated, the more gain he will have by the end of it. Meaning they could accidentally kill each other and lose that training forever.
Something else that he learned from it was that self-inflicted damage doesn't count but Multi-Form beating does which made Goku think for a while as he can't harm himself for the use of this ability but his clones can for each other. Eventually, he gave up on trying to understand it and concluded that it was the logic of this reality.
Goku assumed that all Saiyans have this trait and was most likely the reason why they were called the strongest warrior race. If so, then there was no way that the Saiyans have not dominated the universe yet. Unless there was something either kept them in control or the Saiyans themselves were weak.
Anyway, that's how the past 6 months went for the Goku clones with their physically abusive training. Not only did their general power increase but the Breath of Life leveled up as well. Naturally, the Fist of Flowing Water improved due to the amount of practice the clones put in and the level of experience they were gaining by applying their knowledge to actual practice. Even better was the fact that both Goku clones were using the same martial arts so it taught them their flaws and areas of improvement quite efficiently.
As this martial art emphasizes perfect defense and perfect offense, it became harder to deal damage to the other but at the same time, it also became easier. The Goku clones could just let the other beat each other but then he would have to bear a great deal of physical pain. Not to mention, his Saiyan power could not be abused for increased leveling of his skills. Every time, he could tell when this martial art or his technique just stop growing unless normal fighting happens for a certain period and then he could go through his self-torture.
On another hand, with his Breath of Life leveling up, he got different benefits per level with each benefit being active together whenever the Breath of Life is being used. The technique won't give him any information about it so he had to figure each one out by himself. So far, he knows that at level 1, his Ki quantity and quality increase every time this technique is utilized but another thing he figured out was that it also improved his skeletal and muscle system slightly. Now he knew that the first two boosts automatically improve his body but the third benefit was independent of the Ki so, in a strange way, his physical prowess was still increasing. Next, at level two, he realized that now all his organs improve marginally and his stamina slowly gets restored with every use. The small stamina recovery does help with fatigue with a low level of effectiveness but he was sure that it would be more useful in the future. Perhaps it can be enhanced and it would allow him to use more of his time doing something.
Goku(4): "Time. Go get us some water and some food while I check our progress." he said.
Goku(5): "Alright." Goku replied as he swiftly flew away. The Goku clones started focusing on his mind.
[Fist of Flowing Water (Level 3)]
[Breath of Life (Level 3)]
[Multi-Form (Level Max) (Enhanced)]
[Ki to Body Channeling (Level 7)]
[Vast Energy Forms and Manipulation (Level 27) - With Variations]
Goku(4): "Great! Breath of Life just leveled up. Let's see what the benefits are." he thought as he activated the technique. He felt a change immediately. The range of his Breath of Life went from a small area to an entire city. Since one Goku leveled it up, all Gokus leveled up too. When the police officer Goku used the technique, he noticed that it covered all of West City and a little more. Satisfied with the results, Goku(4) continued polishing his martial arts and his energy.
Turns out, every Ki style attacks that he has ever done has been classified into one technique in his mind. So the Vast Energy Forms and Manipulation contains all his Ki blast, Ki waves, Beams, his Kamehameha, Dragon Fist, and all others. Leveling up this technique increases his efficiency, energy consumption, and control of every Ki attack. A great example would be the Kamehameha as it now can be used in one hand and doesn't need two hands to concentrate it. Although, with two hands, it becomes 50% stronger and is conjured faster.
Ki to Body Channeling was a little different from the rest as it uses the Ki to enhance physical strength and doesn't bring it out the body. With this technique increased, it allows him to know how much his body can handle his own Ki along with making his body having a better affinity to it. Thus effectively improving how fast his Ki can travel in his body and how much can be stored in a single part of the body. This was the unique aspect of this technique as most warriors that use Ki evenly distributes it throughout his or her body and can only focus their energy at one point to launch an energy attack like the Kamehameha.
For example, with the Ki Fist that he attacked Raditz with. If he had to compare a Ki Fist that he can make now compared to the one in the past, he could see that the power between the two is drastically different. Not because of his increase in Ki quality and Ki quantity but rather because his body can handle more. Goku estimated that at level 10, his body would be able to handle 5 times his power at a single point.
It is unknown to Goku for now but as he transforms in the future, this technique will not limit him or clash with him as this technique is exclusively used for focusing Ki in parts of the body rather than the entirety. The Breath of Life and his own Ki does that, not anything else. This technique also had the additional passive benefit of letting him handle sudden increases in power without any discomfort or pain unless it exceeds the limit this technique has imposed on his body or is natural. Hence, Ki affinity.
Goku(5) came back and talked to himself enthusiastically. With the new range of the Breath of Life, their upgrades will come sooner and becoming stronger will become a breeze. Once they were done with lunch, they continued the training until two in the morning. It wasn't until they were dead tired did they realize what the 3rd level of the Breath of Life gave them; an increase in endurance. Being happy with the progress, they decided to sleep for the night and get some grub tomorrow.
[Capsule Corporation]
Bulma: "You know. When you walked in six months ago and asked me for a favor, I didn't think that it would lead to this." she remarked with astonishment. What she was witnessing right now was the birth of a genius. Goku went from uneducated to starting college in a single week. Not to mention there were two of them that did it at the same time. Surprisingly, his basics are much more solid than hers in all subjects.
Goku(4): "Well. It wasn't that hard."
Goku(5): "Yeah." Bulma felt her eye twitch at the casual statements. She thought that she was a genius but Goku proved her wrong very quickly. It was so weird for her. She felt like today, she woke up in an alternative universe or something.
Bulma: "So what now? What are you going to do with your GED?" she asked.
Goku(5): I am going to be a police officer while he is going to be a teacher. "He responded as he pointed at the other Goku. Bulma raised her eyebrows at his statement.
Bulma: "Wait wait wait. I understand the police officer but how could you possibly teach kids? You have no experience with other children."
Goku(6): "And that's why there are high schools and colleges." He smiled before going back to his studies.
Bulma: "..." She stayed quiet at that statement and let out a sigh. "Okay, Goku. Do your best I guess." she said before turning around and leaving. Goku then called out to her.
Goku(5): "Sorry for asking you the favor. I know that giving that much money must have hurt your wallet. Not to mention using your connections." He genuinely apologized as he showed a little bit of guilt in his eyes.
Bulma: "It's fine Goku. You're one of my best friends and you saved me and this planet more than I can count so It's the least I could do for you." She smiled.
Goku(5): "I'll pay you back. I promise."
Bulma: "You don't have to worry about it Goku. I don't care much about money." she said as she left.
Goku(4): 'She's really...' He mentally sighed. 'She seems so perfect...'
Goku(5): "Don't even think about it. Focus on your studies." he shouted for Goku(4) to hear. This brought Goku(4) out of his mind as he continued his task. 'This is going to be a disaster in the future. I can almost already see it.'
...