In whatever world it may be, talent plays a huge factor in determining one's competency.
Bloodline Limit, also known as the kekkei genkai. It is said that in the world of ninjas, the weapons that they were innately born with provide myriad advantages that are, in most of the cases, impossible to overturn.
There are many types of Bloodline Limits. Among them, the Ocular Bloodline Limits, dojutsus, are commonly referred to as one of the finest Bloodline Limits that one can ever be born with, if not the finest.
Notably, there are the Sharingans of Uchiha Clan and the Byakugans of Hyuga Clan. Interestingly, their ancestry is rumored to have originated from none other than the legendary Sage of Six Paths himself, the one and only known wielder of the almighty Rinnegans.
Thus, everyone assumed, that whatever this Rinnegan may be about, it must be stronger than even what Sharingan and Byakugan are capable of.
...Never did Akashi expect to face against such a dojutsu, in the illusory world, against his mirror self of all things.
Just from a short interaction, Akashi identified numerous abilities of the Rinnegan.
Gravity manipulation. Chakra-enhanced, jinchuriki-like healing factor. Bizarre growth of limbs. Diverse ninja summons unheard of. Ninjutsu nullification and corresponding chakra absorption.
Akashi assumed that there must be more that Rinnegan is capable of. The reason that his other self didn't reveal other abilities, probably, is because they have detrimental side effects or are irrelevant to scenarios that involve battles.
However, this didn't mean that the case was hopeless.
Among many troubling powers of the Rinnegan, Akashi managed to find a way to counter the most bothersome one, the chakra absorption, through the instantaneous usage of senjutsu.
The Sage Mode of his is essentially nothing more than the modification upon the nature of his chakra through the reconfiguration of its components. This simple yet difficult feat results in the chakra of a violent nature that would tore anyone else apart from the inside should it be absorbed. It could be said that this modified chakra is the very embodiment of the nature.
"Clearly, you would want me to absorb that toxic chakra of yours..."
The foe remarked, flicking his wrist casually as he said so.
"I see that it is the game of speed that you want me to commit. However, why should I?"
Akashi watched as the foe formed a hand seal.
Summoning jutsu.
Gigantic puffs of smoke enveloped the site following a huge exertion of chakra out of the foe.
Some of the largest ninja summons that Akashi ever saw throughout his life filled the scene, surrounding him from front to back.
"It is obvious that no matter how proficient you may seem in utilizing that technique, there must be a condition. There must also be a cost of some sort."
His other self was referring to his Sage Mode.
...To some extent, his other self wasn't wrong.
The difficult part wasn't really about entering the Sage Mode, but rather, maintaining the 'Yin-abundant condition' that was a prerequisite to it.
Due to his extreme Fire affinity as well as his status as a male, Akashi's constitution was naturally shifted toward the side of Yang, quite heavily so. It could be said that without an outside factor, it is nigh impossible for the current him to reach the 'Yin-abundant condition.'
"Akashi... is everything good?"
The key to reaching this condition was none other than Chakka, who was, for some reason, extremely Yin-skewed. This also gave Akashi a suspicion that Chakka may be, should the moth have a gender, a female.
Nevertheless, Akashi knew that given the Rinnegans that his other self possessed, it was the matter of time before he noticed Chakka's presence in Akashi's cloak. Once Chakka has been identified as the weak point, the stakes may be weighed in the favor of his foe.
In a way, they were already in the battle of speed that his other self mentioned, except that it wasn't exactly the same as what he may have imagined.
"Try to keep up if you can... with my game, that is."
His other self stated.
Now, the crimson moon illuminated all that lied underneath with its equally crimson moonlight. The contrasting shadows of gigantic summons all around Akashi enclosed his world into that of a pitch black, and all that could be seen in his lone eye were just as gigantic pairs of Rinnegans attached on said summons.
Jaws gaped open, claws brought down, spikes approaching—all sorts of attacks were thrown at him in an instant.
Within this nightmare-like scenery that the running-away civilians and ninjas of Konohagakure shuddered upon taking a peek, Akashi released his hold over Ryuma.
Ryuma, once again, flew out of his grasp. Glowing in green, it moved as if possessing the will of its own and danced through the darkness, penetrating all the Rinnegan-possessing creatures that dared to threaten its master.
Spirit Blade.
"Energy Release... yes."
Witnessing the scene, the foe frowned.
"The fruition, the ultimatium, of Shizen Clan's research."
As the ninja summons all dispelled and filled Akashi's surroundings with smoke once more, the foe spat bitterly,
"You have no idea for how long I attempted to manifest the ability after the revelation. It indeed was the revolutionary resesarch, for Energy Release is the power to overcome the Bloodline Limit with nothing but grits."
The foe raised his right hand. On top of his palm, a faint green light appeared, although it looked unstable.
"However, my pool of chakra was simply too gigantic. No matter how much the Rinnegan assisted me in the aspect of the chakra control, it was impossible for me to use Energy Release... isn't that amusing? The fact that because I was too talented, I wasn't able to train that technique?"
Ryuma returned to Akashi's grasp. Cutting through the smoke, Akashi walked out, cold-faced.
"Is that so?"
As Akashi said, his eye darted to the surroundings.
It was guaranteed that within this gap of time that Akashi spent dealing with the summons, his foe set up a trap that would give him a ground in this fight.
"Heh! Why, aren't you heartless."
Just as Akashi expected, the foe grinned as he raised his hands again, weaving numerous seals at a phenomenal speed that surpassed what Akashi was capable of.
Tiger, Dragon, Monkey, Dog, Ram—
Akashi noticed that there were four other clones of the foe that surrounded him from some distance away. He also noticed that between the clones and him, there were thin network of wires, ready to be manoeuvred to delay his escape.
'On top of that, the smoke was filled with chakra, obstructing not only my vision but also my other senses...'
"Fire Release."
His foe, most likely the original, declared as he completed his series of hand seals.
"Lightning Release."
"Wind Release."
"Water Release."
"Earth Release."
Each of the four clones signalled the use of different natures.
The chakra level spiked, to an extent where Akashi could view the blue hue emanating out of them.
'It seems that...'
Akashi deduced as he furrowed his brows,
'Rinnegan also grants its users an affinity to all five elementary natures.'
In the next instance, all five of them spat out huge waves of fire, lightning, wind, water, and earth at the middle, where Akashi stood. Within a split second, Akashi's vision was filled with a chaotic mess, and out of instinct, he reacted.
With a boom, the elements collided viciously. A vortex of calamity manifested, disintegrating whatever lied within.
Then, they magnificently exploded along with a thunderous noise that frightened whoever was able to witness the scene.
It was akin to the judgment of a divine being.
"Hmph."
Lowering his hands, Akashi's other self smirked with a satisfaction as he stared at the smoke-filled scenery in front of him. Meanwhile, his clones dispelled, for they fulfilled their duties.
"Each ninjutsu, of differing elements, was an A-rank in terms of its potency. No matter how—"
Swoosh.
Then, his Rinnegan eyes widened.
Lowering his head, he found a deep, diagonal gash across his chest.
The blood sprayed out as he slowly turned his head.
"What..."
There stood Akashi, who stared back at his foe with not only the lone grey eye that indicated his use of Sage Mode, but also the Lightning Release: Chakra Mode. The crackling noise of the electricity broke the silence.
And that was just the start.
Turning, Akashi stabbed his other self in the wounded chest with Ryuma that was imbued with a senjutsu chakra.
"You're right."
In this state, Akashi remarked as long grey eye met a pair of Rinnegans,
"It is, in the end, the battle of speed."
On his left hand, rasengan swirled into the appearance.
Gritting his teeth, the foe raised his hand to absorb the spiralling orb of chakra, only to realize that he couldn't, for the blade embedded into his chest was injecting the senjutsu chakra that was violently thrashing from his inside.
It was a misjudgment, a kind of mistake that Akashi would never make. Such a mistake showed that this alternate version of himself, whether he like it or not, had his battle sense be rendered dull, due to the conveniency that Rinnegans gave him.
Thus, the rasengan managed to drill its way through the outstretched arm of the foe, shredding it into countless pieces of bloody lumps. Akashi's mirror self's face morphed into that of an agony, although he gritted his blood-stained teeth and endured the excruciating pain.
Within this couple of seconds, the foe was reduced into a bloody state, barely alive by sight.
Swiftly pulling Ryuma out as the Sage Mode and Lightning Release: Chakra Mode simultaneously died within him, Akashi retreated a few hundred metres away.
Immediately after, there was an enormous explosion centring the foe, indicating the strong use of Almighty Push.
'The injuries I gave him are critical.'
Akashi pondered as he observed the foe who, although bleeding and panting, hasn't yet fallen.
'A simple healing factor won't do the work. If he can recover from even this... it isn't the simple healing, but an instantaneous cell proliferation and scar tissue production... which is, ultimately, one of the hypothesized abilities of Yin-Yang Release.'
And based on the speed of his other self's recovery, it looked like such was the case.
This confirmed that aware or not, Rinnegans granted its users the ability to utilize Yin-Yang Release on top of all the abilities that Akashi has seen so far.
'Yet, he doesn't have any tolerance against the Yin-Yang-senjutsu that I injected into him.'
However, that didn't mean that the foe was immortal.
Within this short interaction, Akashi noticed that his foe was protecting his brain. Such was the reason why he targeted the heart instead of the head.
He supposed that it made sense. After all, without a capability to think and recognize the danger to one's state, no healing or usage of jutsus will be made. It could be said that to this Rinnegan wielder, brain is his sole fatality.
"But..."
"Yes."
Chakka murmured, and Akashi nodded.
"He won't fall for the same trick twice."
The fact that Akashi's foe was unable to predict Akashi's use of 'Lightning Release: Chakra Mode' of Raikage meant that he was incapable of using it, unlike Flying Thunder God. Perhaps, this world's Raikage didn't possess such a technique for his other self to observe and copy.
It was thanks to the amplification of Akashi's physical capability through the combined efforts of Sage Mode and Lightning Release: Chakra Mode that he was able to find his way out of the complex network of wires on top of the storm of ninjutsus, without teleporting to the Flying Thunder God kunai that his other foe was likely expecting him to use.
"I have a couple more tricks left in my sleeves to exploit. Problem is that it is likely the same with him..."
Letting out a breath and recovering from a momentary fatigue that followed after the simultaneous use of two advanced techniques, Akashi saw that his opponent has mostly recovered—although he wasn't able to mask the exhaustion that filled his facial expression.
"Thankfully, it looks like he isn't fully healed, thanks to the aftermath of the senjutsu chakra I left in him."
Akashi thought of the ongoing disasters in the actual world. He remembered the masked man's act of locking Konan into this world of genjutsu.
'Are you watching, Uchiha Madara?'
Solemnly, Akashi narrowed his eye as his foe, who no longer looked as relaxed, formed a familiar hand seal to launch yet another attack.
"Shadow Clone."
With puffs of smoke, hundreds of physical replicas filled the barren ground.
They simultaneously charged at Akashi, presumably to buy their original more time to recover.
Without a further thought, Akashi dashed once more, toward the army of his alternate self.