Itachi remembered the memories of the day when Shisui had explained the true nature of his famous jutsu to the original Itachi.
In those memories the real Itachi had listened with careful attention yet he had never set aside the time to learn the technique himself.
Itachi found that choice almost foolish.
A jutsu of such power had been offered freely by a trusted friend and the only reason it remained unlearned was the lack of wind nature training.
The decision felt like a waste when viewed through the eyes of someone who now possessed fifteen years of uninterrupted practice time.
—Flashback— The training ground was quiet save for the gentle rustling of leaves in the afternoon breeze.
Shisui stood atop a wooden post with his hands tucked loosely into his pockets while a young Itachi watched him from the ground with focused eyes.
The three tomoe of the younger boys Sharingan spun in a rhythm as he studied every small movement his older friend made.
Itachi spoke first with curiosity, “So everyone says you teleport from place to place in the middle of a fight.
But you do not actually know the Flying Thunder God Technique that the Fourth Hokage made famous.
That much is clear from the way the clan elders speak about you.” Shisui chuckled softly and the sound held no pride only quiet amusement.
“No.
If I could truly teleport the way Minato sama did then the Fourth Hokage would probably be out of a job.
What I do is something different and in some ways more practical for battles.” Itachi frowned and tilted his head slightly.
The answer had not satisfied the puzzle that had bothered him for months.
“Then how do you disappear so completely that even other Uchiha lose sight of you?
The body flicker most of us use still leaves a blur that a trained eye can follow.” Shisui hopped down from the wooden post and landed lightly on the grass.
“The reason is that most people misunderstand speed itself.
They believe that strong muscles and quick legs are the only things that matter.
They are wrong.
Muscles are important but they are not the whole story.” He lifted one finger and tapped the empty air in front of him as if pointing to an invisible wall.
“The greatest enemy of speed is not your own body.
The greatest enemy is the world that surrounds you every time you move.” Itachi tilted his head further the confusion clear on his young face.
“It is not the body?
Then what part of the world stands in the way?” Shisui continued with the calm patience of a teacher who enjoyed the lesson.
“The air itself pushes against you every time you try to move forward.
The ground steals a little of your momentum with every step your foot takes.” “Every turn you make costs precious speed because your body must fight its own direction.
Every landing sends a small shock through your legs and that shock slows the next movement.
All of those small barriers add up and keep a shinobi from reaching true speed.” He smiled and finished the thought with quiet pride.
“And that is exactly why my Wind Release: Phantom Wind removes those obstacles one by one.” A faint layer of transparent wind wrapped around Shisuis body like a second skin.
The grass around his feet bent outward in a perfect circle even though no natural breeze was blowing.
The air itself seemed to lean away from him.
“The first thing my jutsu, does is split the air before I ever reach it,” Shisui explained.
“Instead of crashing into the wind and pushing it aside with raw force the wind simply moves out of my path on its own.
I am removing the resistance that every other shinobi must fight with every step.” Itachi watched the bent grass and spoke the conclusion that formed in his mind.
“So there is nothing left to slow you down once the jutsu is active.” “Exactly,” Shisui answered.
“Most shinobi waste large amounts of chakra trying to move harder and faster against the air.
I waste little of my chakra fighting something that no longer stands in my way.” In the next instant Shisui disappeared.
A soft gust of wind swept past Itachis face and ruffled his dark hair.
The younger boy turned on pure instinct and found Shisui already standing behind him with the same relaxed smile.
“The second part of the technique is propulsion,” Shisui continued as if he had never moved.
Tiny spirals of wind formed for a brief moment around his calves and then vanished again.
“Every time I take a step compressed wind bursts behind my legs and along my back.
My muscles push once and the wind pushes a second time in the same direction.
The two forces work together.” Itachi nodded slowly as the meaning became clear.
Shisui lifted one foot from the ground and held it in the air so that Itachi could see the faint swirl beneath the sandal.
“The third part is the control of friction.
A thin layer of rotating wind forms beneath my feet.
My sandals barely scrape the earth when I move.
Because less energy is lost to the ground with every step it becomes easy to accelerate and easy to keep that speed once I have it.” Itachi searched for the right word.
“So you are almost gliding across the surface instead of running on it?” “Close enough,” Shisui said with a small laugh.
To prove the point he darted left then right then straight backward.
Each change of direction happened in an instant.
There was no visible pause between one movement and the next.
Itachi murmured the observation that troubled him.
“There should have been a pause when you changed direction.
Every body flicker jutsu, I have ever seen needs a moment to stop the old movement before the new one can begin.” “There usually is such a pause,” Shisui agreed.
He pointed to the swirling wind that still moved around his waist.
“When a shinobi changes direction the body must first overcome its own momentum.
That is the biggest limitation of the standard body flicker.
My technique does not carry that limitation.” Itachi finished the thought in a quiet voice.
“The wind itself pushes you into the new direction so that you never have to slow down first.” “Exactly,” Shisui said.
“My jutsu redirects the air around my body and creates sideways thrust the moment I twist.
Instead of slowing down before a turn I am accelerated into the next movement.
The result is continuous speed even when the path changes many times in a single second.” Itachi asked the practical question that any careful shinobi would reach next.
“Then how do you stop without destroying your legs?
Speed of that level should smash bones if it ends too suddenly.” Shisui laughed at the sharp thinking.
“I was wondering when you would ask that question, little genius.
It is the part most people forget to consider.” He turned and sprinted toward a large boulder that stood at the edge of the training ground.
Just before the moment of impact he stopped completely.
There was no skid of sandals on dirt.
There was no crack of stress in the earth beneath his feet.
Only a soft gust of wind flowed past him and faded into the grass.
“The wind reverses its direction,” he explained.
“Instead of pushing from behind it pushes from the front with equal force.
The opposing wind slows the body in a smooth and even way.” A final puzzle remained and Itachi gave it voice.
“Then why does everyone who faces you claim they see multiple copies of Shisui moving at the same time?” Shisui looked toward the distant tree line as he answered.
“I never create afterimages on purpose.” Itachi showed a trace of surprise.
“You do not?” “No,” Shisui said.
He swept one hand through the air and for a brief instant the space shimmered.
“The wind I leave behind creates disturbed currents in every place I pass.
Light bends when it travels through those moving currents.
The people who watch me see distorted images of the place where I stood only a heartbeat earlier.
By the time their eyes and minds decide which image is the real one I have already moved somewhere else entirely.” He finished the explanation with a small smile that held both pride and fondness for his self created jutsu.
“I took the first inspiration for this jutsu after hearing about the Raikages lightning cloak.
You can call my version, a wind cloak that serves only one purpose.
It increases speed and nothing else.
The lightning cloak improves strength speed and defence all at once but it costs a huge amount of chakra.
My wind cloak uses very little chakra in comparison.” “Also, I can use it only because the Sharingan slows my perception of time and lets me see every small change in the air while I move.” Itachi stared at his older friend for a long moment before he spoke the only conclusion that felt honest.
“You are a terrifying genius.” Shisui placed both hands on his hips and gave a smug grin that was only half serious.
“I know.
The elders of the Uchiha clan keep trying to find the flaws in my methods but unfortunately for them I am still looking for those flaws myself.” Itachi answered with a completely flat expression.
“Your humility perhaps?” Shisui scratched his cheek and looked mildly embarrassed.
“Ah.
I knew I forgot something important.” —Flashback End— The memory faded and Itachi returned to the quiet grass of the Tsukuyomi world.
He sat with the full explanation still clear in his mind and reached a simple judgment.
If he was being honest with himself he would classify Shisui as a much greater genius than the original Itachi had ever been.
The older Uchiha had taken ideas that belonged to the study of aerodynamics and friction and had turned them into a working shinobi technique in a world that possessed almost no formal knowledge of such subjects.
The result was a jutsu that did only one thing yet did that one thing better than almost any other speed technique in existence.
Sometimes pure speed was the strongest offence and the strongest defence a fighter could own.
Itachi held no doubt that the Phantom Wind jutsu would be ranked as an S rank jutsu the moment it was fully understood by the rest of the shinobi world.
And how fitting it would be that the very first S rank jutsu mastered by this new Itachi would be the one created by the best friend whose death had brought him into this body.
———Author Notes——– Thankyou doompie for supporting me!