Wind Release: Vacuum Blade.
A B-rank Wind Release ninjutsu that allows the user to infuse wind-natured chakra into a kunai, forming a sharp, extending blade of air.
Its characteristics include relatively low chakra consumption, very few practitioners, and extremely high learning difficulty.
While ninjutsu power isn't strictly tied to rank or base chakra cost—being more dependent on the amount of chakra a ninja invests—higher-ranked techniques, due to their complexity, typically require greater chakra control and expenditure than lower-ranked ones.
But there are exceptions.
Wind Release: Vacuum Blade is one such ninjutsu. Its B-rank classification stems primarily from its difficulty to master. In terms of pure chakra consumption, it is lower than many C-rank techniques.
This is determined by the form the technique takes.
It combines the shape transformation properties of Wind Release with a strong adhesion effect to a physical object.
This "strong adhesion" is similar to the state Asuma Sarutobi would later describe to Naruto: attaching Wind Release chakra to a chakra blade to dramatically enhance its cutting power. Normally, achieving such an effect requires an advanced level of Wind Nature training and a weapon made from special chakra-conductive metal.
This is why the technique, while not outwardly flashy or possessing overwhelming destructive power, is still classified as B-rank.
However, for Shinji Hyuga, with his severely limited chakra reserves, this was the most suitable offensive ninjutsu he could hope to acquire.
The three core skills of the Hyuga clan are the Byakugan, the Gentle Fist, and the Eight Trigrams Palms.
Their underlying principle is the same: utilizing the Byakugan to see the chakra pathway system, then releasing chakra—either continuously or in concentrated bursts—from the body's tenketsu points. This forms the unique, non-replicable Gentle Fist style of the Hyuga.
This system is predicated on Hyuga clan members possessing chakra levels at least slightly above the average ninja.
However,
Shinji Hyuga, while maintaining his Byakugan activation during battle, found his chakra expenditure already significant. The remaining chakra was insufficient to fuel the continuous or large bursts required for advanced Gentle Fist and Eight Trigrams Palm techniques.
During last year's Chunin Exams, he had lost precisely because he ran out of chakra mid-way through executing the Gentle Fist: Eight Trigrams Thirty-Two Palms.
But,
Thirteen years of dedicated study had not been in vain. Shinji had long ago planned his own path to growth.
His limited chakra reserves dictated a combat style that was swift and efficient; his battles would have to be decided in an instant or within a very short timeframe.
Therefore, he had shifted his focus to taijutsu, ninja tools, and medical ninjutsu, aiming to combine them with his Byakugan to create his own unique combat system.
And now, the final missing link in this combat system was...
This Wind Release ninjutsu:Vacuum Blade!
Shinji had not initially intended to acquire the technique in this manner. His original plan was to rely on his own deepening understanding of Wind Nature Transformation to eventually develop his own, slightly weaker version—a C-rank technique.
The price for acquiring the genuine article was simply too heavy.
However, plans often change.
With things having come to this point, in order to protect his fiancée Hyuga Natsu and to survive the battlefield he was about to enter, Shinji Hyuga had no choice but to take this step ahead of schedule.
Wind Release was a rare affinity among ninjas.
Within that already rare group, as far as Shinji knew, there were only three ninjas who had mastered the Wind Release: Vacuum Blade technique.
In the entire Hidden Leaf Village, there was only one person—
Shimura Danzo.
After pondering for a moment and solidifying his plan, Shinji Hyuga walked out of the Hokage Building after posting the mission. He identified his direction and then ran without pause towards the Konoha training grounds.
If the village layout was fan-shaped,
The Konoha training grounds were located on the outer rings of this large semi-circle,near the village walls and surrounding forests.
The supporting ninja tool shops,blacksmiths, and various supply markets were all clustered in this area.
It would take some time for the news of the S-rank mission posted by Shinji Hyuga to circulate and reach the relevant parties.
(T/N:In reality, the mission's difficulty might be closer to A-rank, but due to the special wartime circumstances and the high reward, it was registered as S-rank.)
Using this window, Shinji came to this district to retrieve a "secret weapon" he had been preparing for a long time.
The streets outside the training grounds were bustling with activity, filled with ninjas purchasing tools and repairing equipment.
Shinji moved through the crowd, lifted the noren curtain, and entered a large ninja tool shop.
A young apprentice, responsible for running errands and attending to customers, immediately perked up upon seeing Shinji's distinctive eyes. He eagerly approached.
"Welcome! Honored customer, how may I assist you?"
Shinji glanced at the boy, noting his topknot and round glasses—clearly a new face he hadn't seen before—and said:
"I've come to pick up a ninja tool I commissioned."
The apprentice immediately scurried to the counter, searching through the scrolls recording custom orders. He flipped through several but couldn't find the surname "Hyuga." He looked up somewhat sheepishly, his face flushed.
"Customer,when did you place the order?"
"Not in those."
Shinjishook his head and pointed to a scroll at the very bottom of the pile.
"Look there.Eight years ago, a ninja academy student named Shinji Hyuga commissioned a ninja tool from this shop."
"Eight years ago?" The apprentice was stunned.
He hadn't even been born eight years ago.The Hyuga boy in front of him would have been only six or seven at the time.
What kind of ninja tool took eight whole years to make?
And how useful could a tool designed for a 6 or 7-year-old possibly be now?
"Please wait a moment!" Realizing this was important, the apprentice didn't dare delay and resumed his search.
Just then, a rough voice boomed from the backyard of the forge.
"Nitro—!"
"What are you dawdling for?Where's the ore I asked you for?!"
"Y-Yes, sir!" The apprentice—apparently named Nitro—jerked his head up at the voice.
"Master Sulfur,I'm coming right now!"
"Too slow! Too slow! And did you not eat? Put some more energy into it! How can such a weak voice forge powerful ninja tools?!"
As the voice echoed, an older man with a receding hairline peered out from behind the inner room's curtain.
SeeingShinji Hyuga standing in the shop, the man named Sulfur blinked, feeling the boy looked familiar, but the image didn't quite connect.
"Hey, you there... you look familiar..."
Seeing him, Shinji smiled slightly and offered a greeting.
"Master Sulfur,it's been a long time."
Sulfur.
This man was one of Konoha's premier ninja tool smiths.Eight years ago, Shinji Hyuga had spent 100,000 ryo to commission him to create a unique weapon.
"Oh! I remember now! You're the Hyuga boy. I saw your matches in last year's Chunin Exams; your use of ninja tools was impressive... it's just a pity..."
Sulfur then recognized Shinji, his face showing dawning realization. But as if remembering something, he quickly shut his mouth, looking awkward.
"My apologies..."
"It's fine."
Shinjishook his head dismissively. He had only awakened his Byakugan two years prior, and his proficiency with medical ninjutsu and Gentle Fist techniques was still at a foundational level.
Chunin weren't cabbages;making it to the final tournament under those circumstances had been incredibly fortunate.
However, things were different now.
Thinking this,Shinji looked directly at Sulfur and asked:
"Master Sulfur,how is the ninja tool I commissioned coming along?"
Looking at the boy before him, Sulfur immediately recalled the 'special ninja tool' commissioned eight years ago. His spirits lifted, and a proud smile spread across his face.
"That ninja tool is finished!"
"We were just completing the final tempering process last year,so it couldn't be delivered. My sincerest apologies!"
As he spoke, he beckoned for Shinji to follow him into the backyard.
"Come with me!I promise, it will not disappoint!"