Chakra control was easy enough to fix. He could simply toss the two basic exercises, "Tree Climbing" and "Water Walking," into his passive skill slots and let them run, quickly grinding up their proficiency.
But the drain on his mental energy wasn't something Tree Climbing and Water Walking could compensate for.
With a thought, Lei Dou temporarily unequipped "Fire Release" and "Water Release" from his skill slots.
He casually equipped "Tree Climbing" and "Water Walking" instead. As a transmigrator, he already knew these two basic skills inside out.
As for my lack of mental energy, I'll probably have to work on genjutsu!
Lei Dou had already found time to analyze the basic genjutsu scroll Shimozuki Hayate had given him using his active skill.
He just hadn't freed up a passive skill slot to test its effects.
Now, he decisively cleared one Chakra Extraction Technique slot and replaced it with "Basic Visual Genjutsu."
He silently counted the seconds.
In less than five seconds, the system notified him that the skill had completed one cycle.
By comparison, Tree Climbing and Water Walking each took roughly seventeen seconds per cycle.
The speed at which this genjutsu ran was astonishing.
Lei Dou began carefully sensing the changes in his chakra control, while also checking whether running the genjutsu could actually nourish his mental energy.
Although this was his theoretical conjecture, that didn't mean it was necessarily correct.
A full thirty minutes passed before the bell finally rang to end class.
The four of them received another stern scolding from the still-furious Iruka before being allowed back into the classroom.
As soon as he returned to his seat, Lei Dou laid his head on his desk and resumed pretending to sleep.
In reality, he was fully focused on monitoring whether his mental energy was increasing.
Sensing mental energy directly was rather abstract, so Lei Dou checked indirectly by manipulating water- and fire-nature chakra as it flowed through his chakra pathways.
Sure enough, that sluggish resistance was gone. Controlling it was much easier than before.
However, Lei Dou discovered that his active skill hadn't begun analyzing a new nature transformation.
That meant basic genjutsu alone couldn't directly grant him the nature transformation for "Yang Release"'s counterpart, "Yin Release."
My mental energy really is growing. That proves genjutsu definitely has a connection to Yin Release!
But why can't the skill analyze the Yin Release nature?
Lei Dou's mind raced as he considered the key to the problem.
Could it be because this is only Basic Visual Genjutsu? Is its level too low to reach the threshold for Yin Release nature transformation?
For now, that seemed to be the only reasonable explanation.
If basic genjutsu wasn't enough, what if he got his hands on a high-level genjutsu?
That should give him a chance!
Lei Dou already had a clear idea of how to acquire the nature transformations for the five basic natures.
The only challenges left before him were the mysterious Yin Release and Yang Release.
For Yin Release, Lei Dou suspected genjutsu was the key.
As for Yang Release, he suspected advanced medical ninjutsu such as the Mystical Palm Technique might help him open that door.
High-level genjutsu and the Mystical Palm Technique... neither of those is something you can find just anywhere!
High-level genjutsu was a scarce resource, and the Mystical Palm Technique was an even more demanding skill, with S-rank difficulty.
There was no way scrolls for ninjutsu like that would circulate on the market.
Without a skilled teacher providing hands-on instruction, learning from a scroll alone was a pipe dream.
To learn the Mystical Palm Technique, he would either have to get into Konoha Hospital or find a veteran medical ninja willing to take him as an apprentice.
Despite all the difficulties, Lei Dou would never give up on these two most unusual nature transformations.
As Basic Visual Genjutsu continued running in the background, Lei Dou felt his mind becoming clearer and his mental energy more abundant.
That refreshed, clearheaded feeling was further irrefutable proof: genjutsu really could nourish mental energy.
With genjutsu boosting my mental energy and taijutsu strengthening my body, I'm essentially increasing my life energy indirectly.
With stronger life energy, the Chakra Extraction Technique's efficiency will naturally rise too.
It looked like taijutsu and genjutsu would have to become permanent fixtures in his skill slots from now on!
After school, Lei Dou didn't go straight home. Instead, he bought some food from a roadside stall to fill his stomach.
Then he plunged into a small grove on the outskirts of the village.
After "Water Walking" and "Tree Climbing" had been running all afternoon, Lei Dou could clearly feel his chakra responding as naturally as his own limbs.
With his improved control, manipulating water- and fire-nature chakra was now effortless.
At the same time, the genjutsu had boosted his mental energy considerably.
Everything was ready. It was time to try fusing chakra again!
And this time, Lei Dou had a strong feeling that his chances of success were excellent!
"The nature transformations are powerful enough, my chakra control is solid, and I've got enough mental energy!"
"I've finally gathered all three essentials for chakra fusion!"
Lei Dou slowly exhaled and sat cross-legged on the leaf-covered ground.
In theory, nothing should go wrong with this next attempt at chakra fusion.
Even if the nature transformations were still a little short on power, he could just let them run for a while longer.
"Tonight, I have to get this fusion working!"
As long as he could successfully fuse even the tiniest trace, the system could record it as a new ability.
Then he could strengthen it around the clock through his passive skill slots, ultimately completing the kekkei genkai fusion.
With these cheat-like skill slots, Lei Dou only needed to pry open a crack. Time would take care of the rest.
At that thought, Lei Dou closed his eyes and began regulating his breathing, bringing himself into peak condition.
Chakra fusion began!
His previous, weak attempt at water-fire fusion had used only a tiny thread of chakra.
Yet the power it unleashed had still made Lei Dou suffer.
Now both natures had been strengthened, multiplying their power.
Under these circumstances, even a tiny amount of chakra exploding out of control could land Lei Dou in the hospital for half a month if he wasn't careful.
"Safety first. I'll test it with the smallest possible amount of chakra!"
"I have to minimize the total amount of chakra involved in the fusion!"
As for the fusion ratio!
Naturally, he would start with the classic fifty-fifty split: fifty percent to fifty percent!
He would observe the fusion reaction and fine-tune the ratio based on the feedback.
A tiny flame flickered to life on his left index fingertip, so faint that it seemed ready to go out at any moment.
A small, crystal-clear droplet formed in his right palm.
Fully focused, Lei Dou slowly brought his hands toward each other.
The two completely different streams of chakra began touching and intermingling, just as they had last time.
The instant their power made contact, a violent repulsive reaction erupted.
Boom!
This explosion was even more terrifying than the last!
The shock wave surged outward. Lei Dou felt as though a whip had struck his chest. Looking down, he saw that his clothes had torn and two bloody wounds had been ripped across his chest.
Fortunately, he had limited the total amount. The injuries weren't fatal, only flesh wounds.
Lei Dou had no time to care about the pain. His mind raced.
He carefully recalled what he'd felt in that instant. His improved control and mental energy had allowed him to catch more details.
The instant the fusion began, the water-nature power seemed to be suppressed. It couldn't restrain the flames and collapsed outright, letting the fire run wild and trigger the explosion!
He had finally found the root cause of those explosions in his face.
The fire was too fierce for the water to suppress. Of course it exploded!
In that case, I'll reduce the proportion of fire-nature chakra!
He slashed it drastically, down to ten percent.
If it didn't explode this time, even a failed fusion would at least prove that adjusting the ratio was the right approach.
Lei Dou hastily bandaged his wounds and immediately began his second attempt.
Sure enough, after he adjusted the ratio, the flames tried to surge back the instant the two streams of chakra touched.
But the water, now holding the advantage, pinned them down firmly.
The flames had no chance to erupt. Instead, the temperature of the water-nature chakra began rising sharply, becoming scalding hot.
Before long, however, the water-nature chakra could no longer hold out and dissipated outright.
Lei Dou opened his eyes, his gaze flickering.
"No explosion is a good thing, but... it still doesn't seem to fuse perfectly!"
Failure to fuse meant the ratio was still wrong, or the underlying power of the water and fire didn't match!
Still, since the chakra hadn't immediately collapsed, his general approach was correct.
He just needed to find that golden ratio, keep the chakra stable, and then gradually increase its power.
With his direction established, the work that followed became a tedious math problem.
Water to fire!
90% to 10%! Wrong. Too much water.
80% to 20%! Still wrong.
70% to 30%! A small eruption occurred, resembling the prelude to an explosion.
It seemed there was too much fire.
75% to 25%! This time it was much more stable, but it eventually collapsed.
The collapse meant there was still a little too much water.
74% to 26%!
72% to 28%!
73% to 27%. That was it!
This time, the mass of chakra in Lei Dou's hands actually stabilized, lasting a full ten minutes.
Only after ten minutes had the water in his hands completely evaporated, leaving just a few lingering sparks.
Lei Dou froze for a moment, staring at his empty palms, unsure whether this counted as a success.
[Congratulations, host. You have successfully mastered the Water-Fire Nature Fusion Prototype.]
Excellent!
The system's notification sounded like heavenly music, giving Lei Dou a definite answer.
He had found a way forward!
But there had been no notification that he'd acquired "Boil Release," which meant the fusion wasn't perfect enough yet.
Although the water had boiled just now, it hadn't reached the high-pressure state of Boil Release, where steam erupted instantaneously.
That was probably why it had been judged incomplete.
Next, then, he only needed to keep increasing the strength of his fire-nature transformation, and he should succeed completely.
After working all this time, Lei Dou looked up at the sky, then took out his pocket watch and checked it.
It was already two in the morning.
Without realizing it, he had spent seven hours in the grove.
When he focused on one thing, time really did slip by unnoticed.
But that didn't matter. There were still a few hours before dawn, and he had to master Boil Release tonight.
"Now it's time for the passive skill slots to show what they can do!"
[Passive skill 1: Water-Fire Nature Fusion] [Passive skill 2: Fire Release] [Passive skill 3: Water Release] [Passive skill 4: Chakra Extraction Technique] [Passive skill 5: Basic Visual Genjutsu] [Passive skill 6: Konoha Style: Swordsmanship]
His skill slot configuration was complete.
After equipping the new fusion skill, Lei Dou could clearly feel its proficiency soaring as the seconds ticked by.
After patiently waiting five minutes, Lei Dou decided to try again.
This time, the fusion of the two chakra natures was exceptionally stable, harmonious as an old married couple, without any repulsion.
But although he could feel the water-nature chakra continuously boiling and bubbling, the system's notification never came.
Lei Dou could only grit his teeth and maintain that state.
[Great Sage: Notice. Strengthening the water and fire natures simultaneously will cause both to improve in tandem. The flames will never be able to bring the water fully to the critical boiling point.]
Hearing the voice in his mind, Lei Dou slapped his forehead!
That... really did make sense!
A rising tide lifted all boats. If both grew stronger, the gap between them would never widen, leaving them perpetually in this lukewarm state.
[Great Sage: Recommended option one: precisely control the power of the water-nature transformation. Option two: stop running the Water Release skill and increase only the power of Fire Release.]
Of the two options, the first was too difficult for Lei Dou to execute right now. His fine control still needed practice.
By comparison, the second was simple, direct, and highly feasible.
Lei Dou decisively kicked "Water Release" out of his skill slots.
Only "Fire Release" remained, its power increasing furiously.
Ten minutes later!
Hiss, hiss, hiss!!!
Suddenly, the ball of water in Lei Dou's hands began trembling violently, steam erupting wildly like a pressure cooker venting!
The steam that erupted carried terrifying heat, like flames.
At the same time, Lei Dou felt the chakra inside his body begin heating up uncontrollably.
The chakra throughout his body was boiling!
Lei Dou snapped his eyes open, a sharp gleam bursting from them.
[Congratulations, host. New skill acquired-Boil Release]
It worked!!!
Hiss, hiss, hiss, hiss!!
Scalding white steam gushed from every pore in Lei Dou's body, enveloping him in white mist.
At that moment, Lei Dou could clearly feel the violent boiling of the chakra inside him.
It was a high-energy state far beyond the usual gentle flow of chakra.
Lei Dou felt that merely clenching his hand lightly made the sense of power in his fingertips surge severalfold.
Simply maintaining the chakra nature transformation of Boil Release brought such a terrifying increase in his basic attributes.
If I heated all the chakra in my body to boiling point in one go and pushed it to the limit...
How incredible would the power unleashed in that instant be?
Lei Dou stared intently at an ancient tree ten meters away, its trunk so thick that it would take two people to encircle it.
His fingers instantly clenched into a fist. The next second, the steam that had been drifting slowly away suddenly began blasting out in jets.
Lei Dou's skin turned red at a speed visible to the naked eye, like a cooked shrimp.
This was more than a change in his skin.
More importantly, the chakra inside him seemed to have turned into flowing magma, surging wildly through his chakra pathways.
His entire body brimmed with explosive power. The sensation that it might burst his body apart felt absolutely incredible.
With just a light clench of his fist, the veins in his arm bulged and throbbed wildly like vicious centipedes.
As steam blasted from his entire body, Lei Dou stomped his right foot hard against the ground.
Thud! Voom-!!!
The ground instantly shattered, spraying dirt and leaving a large crater as Lei Dou shot forward like a cannonball, trailing an afterimage.