54 Theories 

Unbeknownst to the man that had got gotten a disciple, Azuma was busy in the Yami base, spending time with his mother and sister. As much as Azuma thought he would like his time there, it was not the case, Chikage, was in that period of adolescence, and Mikumo excessively asked about grandchildren.

He couldn't approach Saiga, since he was in disguise, which made Azuma consider talking with the other masters, or their disciples, he mainly talked with Hongō, since different from the other masters, he had mostly calm personality.

But what made Azuma relate more easily with the man was their philosophies, although more extreme than Azuma's, Hongō's thoughts on Katsujinken and Satsujinken were similar, with Hongō being a Katsujinken with non-martial artists, refusing to kill 'normal people'.

The total opposite of Sakaki, Hongō was calm, enjoying the more….educated conversations Azuma likes to have, another reason why he could quickly become friends with Akisame. Regretfully the same could not be said about Hongō's disciples, Shō being a complete pain, with an ego too big for his own good, and the other two disciples, which Azuma didn't bother to learn their names, were simply kissing Shō's ass.

Ignoring Shō, the other disciples were not much better, Rachel tried her best to show off, her brother Ethan following like a shadow, Boris is too soldier-like, Raden Tidat Jihan has an even bigger ego than Shō.

The only two that caught Azuma's attention were, Tirawit Kōkin, mainly for his calm personality, but he tried too hard to behave like his master, which annoyed Azuma. Surprisingly, Satomi Kajima made the biggest impression on Azuma.

The kid was, as Azuma put it, Yomi's Kenichi, he had no unnatural talent for martial arts, actually one may call him untalented, yet, somehow, he gained the attention of two advanced grandmasters, Saiga and Senzui, and while Saiga might have taught him to keep the ruse, he still taught him a little of the Fūrinji style.

But although similar, he is also the opposite of Kenichi; calm, composed and quite intelligent. Azuma even gave him a few pointers in balance and center of gravity, surprising Kajima, as he had learned, like the others, about Azuma's strength.

When he was not getting to know the members of Yami and Yomi, Azuma actually trained, not trained exactly, but more, had conversations with the masters he liked, his mother and Hongō, not trying to give away his plans to either of them, but focusing on his ideas on the application of Dou and Sei ki.

Ki no Shōaku or Holding of Ki, is one of the few dividers between legendary and advanced grandmasters, meaning that there must be a deep understanding of ki to advance to the next class. His plan to reach the class actually focused on his two core styles, Renewal as hand-to-hand, and Hiten Mitsurugi-ryū as sword combat.

In this world, the release of ki outside the body is uncommon to nonexistent, although possible, showcased by his father's fucking Kamehameha, it's only effective against normal people, the technique being literally only used effectively to knock non-martial artist out, meaning, for lack of a better term, it lacks power.

The issue is that Sou ki is the easiest to expel from the body, perfect for Renewal in close combat, but long-range, Renewal and Hiten Mitsurugi-ryū don't need Dou ki, but Sei. Dou is 'explosive' in nature, what Azuma wants is penetrating and cutting power.

So, the plan is to learn how to release Sei ki, a process that done wrong will kill Azuma, Sei ki is the most inward of both, exponentially increasing the difficulty on the already difficult task. But it has the properties Azuma wanted, its calmness perfect for the cutting power he wants if compressed enough. In other words, Azuma wants a laser, not a bomb.

Besides all these reasons, the mastering of ki, as well as having a profound understanding of it would not only help Azuma here but in probably all other worlds. As mainly, most energy, if not all, presented there would-be internal energy, making all training there at least two times easier.

Of course, besides the mastering of ki, reaching legendary class would also unlock Renewal's full potential in this world, allowing him to use his 'forbidden' techniques, not only Soru, and Twin-Dragon Kick, but all the others Azuma had developed during this time.

As for Hiten Mitsurugi-ryū, the main style was copied, but as powerful as it was, it came from a world similar to this, which means that its peak power will not work on other worlds, here is where the release of Sei ki shows it's advantages, Hiten Mitsurugi-ryū is perfect as a base in which Azuma can develop, better-called copy, other techniques, and fuse them with the style.

All of these theories and ideas took years to take their current form, Azuma was starting to make greater progress now, because all failed and infective ideas, were already discarded. He felt something was missing but couldn't pinpoint what.

._._._._._._._.

In one of his conversations with Mikumo

Azuma found himself in the middle of a conversation, in his mother's room, sitting right in front of her. "What could allow one to release ki out of their bodies, not like Dou ki for short distances, but longer range?"

This was the first time Azuma had asked Mikumo that question directly. Much like the others, this one had started with the properties of ki.

With a thoughtful expression Mikumo took a few seconds to answer, "In my opinion, it would all depend, how do you want to release the ki? Which properties do you want it to have? What is the end goal?"

Azuma started thinking, Dou ki could be released and compressed over extremely short distances, the shockwaves his attacks created not being ki, but the air released by the diminutive explosion created by his physical power and when his Dou ki exploded in the air, thus releasing the shockwave.

During all the thinking his talent in physics started to show its advantages, asking his mom, "Ki is energy, correct?"

Mikumo is an extremely smart person, being knowledgeable in multiple different areas, although not an expert, she still knows a bit about a lot of topics, hearing Azuma's question she only nodded, waiting for her son to continue.

"As you know energy cannot be destroyed, then could it be possible that's what is preventing the release of Dou ki in an impactful way is its compression and quantity, thus making it rapidly dissipate."

Mikumo was impressed by this idea, thinking about ki not in a martial arts way, but more in a scientific way, "Plausible, but then following your thought, to successfully do what you want, the amount of ki or compression required would be almost exponential to the travel distance, tiring yourself in one attack if the distance was over a certain range, seems counterproductive."

This was exactly what Azuma had thought of, the explosive nature of Dou ki, believing that the explosive nature of Dou ki to be the main factor in the Ki's quick dissipation, solidifying his thoughts that Sei ki was the option. "Then what about Sei ki?"

Azuma hopped that his mom's answer is different from what he thought, maybe his original theory could be wrong, and an easier solution will present itself.

Thinking that her son may be trying to do something incredibly stupid, again, Mikumo angrily responded, "That would be suicidal, you already know Sei ki tends to flow inwards and Dou ki outwards. To release Sei ki you would need to reverse the flow of the ki, Dou going inside, and Sei outside."

Taking a deep breath, she continued, confirming Azuma's fears, "This would be absolutely necessary since you know Sei and Dou ki do not like to interact with each other, which is the main reason you never see anyone using both at the same time, or combining them."

After another pause, Mikumo finished her thought, "With Dou Ki's properties, trying to make it flow inwards, would kill you."

Not saying anything else about the topic, Azuma only sighed, getting up and leaving, not before telling her, seeing her worry and anger, "Relax mom, the question was purely theoretical, you know I want to enter legendary class. I want to have all my bases covered."

Azuma felt bad about lying to his mom, but her worry would only increase had he told her the truth. This conversation only working to assure Azuma that his theory was correct. He would need to leave the base soon, he isn't sure about the timeline, but he will need to watch Kenichi's fight with Ryūto, as that technique developed by Ogata of fusing Dou and Sei ki, might prove invaluable for his plan.