Time waited for no one and since there would be no further activity until their reinforcements arrived, Shiki decided to get back to his training.
But with the urgency of the current situation, he was going to employ riskier tactics for quicker results.
The boy had been using shadow clones to speed up his training but never too many.
To use shadow clones in this way, one needed two key ingredients, the mental resilience to withstand the mental exhaustion transmitted to the original when the clones were dispelled and enough chakra to make as many clones as possible.
Shiki's Hollow nature made his mental resilience unmatched, Naruto from the series, despite his mental toughness, could simply not compare.
However, the boy estimated that teen Naruto at the time he began clone based training in the Kakuzu and Hidan Arc, had similar chakra potency as him, around S rank but his chakra capacity was likely SS ranked already.
SS rank was marked by Shiki as Super Kage Level. War Arc Naruto with half of Kurama fully supporting him but no Sage of Six Paths amp was claimed by Hashirama to have almost as much chakra as him.
Considering Naruto's chakra reserves should be extremely large owing to his lineage, one can assume his chakra level to be somewhat comparable to half of Kurama so a little less than half of prime Hashirama.
In the Kakuzu and Hidan Arc, a large portion of Naruto's chakra was dedicated to maintaining Kurama's seal, a conservative estimate would be about half and that would still leave Naruto with a quarter of prime Hashirama's chakra capacity to work with.
So if Hashirama was at the very top of SS rank in chakra capacity, it should be fair to place someone with a quarter of his chakra available to them at the bottom of that level.
Needless to say, Shiki with his not even peak A rank chakra capacity could not compare.
So while the boy could mentally withstand the burden of the clones far better than future Naruto, he lacked the chakra to make them in the first place.
However, there was a technique called Tenketsu of Life and Death.
Demonstrated by Guren in the original series, it converted a portion of the user's lifeforce into chakra by activating a few specific chakra points or tenketsu.
Regular Hollows from the Ryumon not only had resilient lifeforce, they also had a lot of it with their lifespan lasting between one and two centuries based on the frequency they use risky techniques that harmed their vitality.
The legendary Dragon God, the mightiest leader his clan had ever known, was said to have lived for over a thousand years.
With chakra added into the mix and possible evolution from integrating aspects of the Otsutsuki, Shiki did not fear expending lifespan to some extent.
And so, using the Tenketsu of Life and Death, the boy converted part of his lifeforce into a large amount of potent chakra, using it to activate the Multiple Shadow Clone Jutsu to create hundreds of clones.
'Not as much as Naruto but enough to condense years of practice into days.' Shiki thought to himself, sufficiently far from any Roran settlement so as to not draw attention in his training.
'My body is still recovering from the abuse I put it through so taijutsu training is off the menu. I'll practice hand seals while the clones take care of the rest. I'll be putting more focus on ninjutsu so this seems like a worthy investment.' The boy decided.
'Part of the clones will focus on Nirvana Art: Elemental and then try to master some basic elemental jutsu to enhance its usefulness.' He began planning.
These jutsu would greatly increase his versatility and if elemental matchups could be exploited, it would be even better.
'Another portion will focus on Yin Release, mainly genjutsu.'
'I've been mostly neglecting it so far but until the alien powerhouses start getting in the mix, it is a powerful tool that could decide battles in one go.'
'The third portion will focus on Yang Release and medical jutsu by extension but with a focus on self enhancement and attack first, healing second.'
'With my young body, my attempts at developing taijutsu will always be limited in either terms of effectiveness or from the amount of backlash I suffer.'
'However, I think I can develop an offensive medical ninjutsu to support a gentle fist type style that will not require a lot of strength or toughness.'
'The fourth portion will go back to Rasengan development, it even gave me inspiration for other jutsu last time so it is definitely worth it to keep going.'
'The final portion will get started on Nirvana Art: Dragon Heart's successor. It will take a lot of time to revamp it and I doubt even the name will be the same after I'm done.'
With his training plan figured out, Shiki threw himself into it, quite literally burning away his life for rapid training progress.
The Shadow clones needed to be dispelled at least once every 24 hours to consolidate the gains before being created again and thus, the boy needed to use Tenketsu of Life and Death multiple times, once every time he reset the clones.
So this kind of training would end up shaving years off Shiki's life but such was the price for the rapid progress he required.
And the results did not disappoint.
Already on the verge of achieving a significant transformation, Nirvana Art: Elemental, was the first to show tangible success.
By eliminating the part of the jutsu that infused elemental power into his own body, the boy had not only made it incredibly efficient, he also managed to complete its initial form.
This new Nirvana Art: Elemental was divided by Shiki into two parts, each having their own development process.
The second part, elementalization of the body, still required deeper research with the Hozuki clan's Hydrification Jutsu being the main target of investigation.
But the first part was much easier, the adaptation of the Yamakaze's Weather Manipulation Jutsu which had already shown results before and only needed refinement from repeated practice.
The boy had been working on it for quite a while now and was hoping to complete its initial form, through the shadow clone brute force method.
When it came to manifesting elemental phenomena from nothing and changing the weather, Shiki needed a long period of focus but manipulating already existing elements was significantly easier.
But the true success was regarding the ability to enhance the user's elemental jutsu using the principles of the Yamakaze's Weather Manipulation.
Previously, the degree of enhancement was not worth the upkeep of chakra that Nirvana Art: Elemental demanded but now, in its basic state, the cost was negligible and the level of enhancement was not only significant, it was obscene.
All this practice raised Shiki's elemental affinities for the five basic natures but they were still at a stage where one could hardly call the boy talented in that area, it was more of a "not a waste of time to train them" kind of situation.
Despite this while under the boost of Nirvana Art: Elemental, his D rank jutsu, the Fire Release: Flamethrower exceeded Mei's C rank jutsu, Fire Release: Great Fireball in power while still retaining the extremely low chakra cost typical of D rank jutsu.
The girl was an Uchiha with naturally very high affinity for Fire Release, even within her clan, her fire jutsu were significantly more powerful than the norm but if both were using the same jutsu with the same amount of chakra, Shiki's would far exceed Mei's in power.
Since his fire release skill and affinity were still pretty low, the boy knew he would struggle with B rank or higher jutsu but he could feasibly start practicing the C rank elemental jutsu he had been memorizing and they would show power akin to A rank jutsu in his hands.
Not to mention, as Shiki's affinities, nature transformation skills and his mastery of Nirvana Art: Elemental increased, this boost would become even more ludicrous.
'But the best part is the low chakra cost, at least for the current me.' The boy evaluated.
His Chakra Capacity was still at mid A rank, Jonin levels, he couldn't go around wasting chakra on big moves, willy nilly.
But with this extreme efficiency, he could finally start practicing and using elemental jutsu in earnest.
+++++
Hey, Author here!
To promote the novel I will be releasing BONUS CHAPTERS on SUNDAYS based on the previous week's power stone count.
100 Power Stones = 1 Bonus Chapter
500 Power Stones = 2 Bonus Chapters
1000 Power Stones = 3 Bonus Chapters
Every earned BONUS CHAPTER on Webnovel will also be posted on Scribble.
Just a reminder that you can read up to a FULL MONTH ahead of this site on pa-treon.
I'm trying to become a full time Author now and I'm not going to be starting any new novels just so I can make sure this one is properly completed.
Find those sweet advanced chapters on pa-treon.com/lusoba without the -