Sengoku returned to their secluded corner of the training ground.
Tetsumaru and Matsufuji were busy throwing shuriken at a battered wooden target, while Kakuda pushed himself through a grueling set of calisthenics nearby.
Noticing Sengoku's approach, Tetsumaru pocketed his remaining shuriken and rubbed a shoulder that was still sore from their morning session. "Yo, you're here. How are we doing this today? Just a heads-up, don't focus purely on my lower body like yesterday. I nearly broke my neck tripping over my own feet."
Matsufuji walked over, his face lit with curiosity. "You first-years just learned the Transformation Technique this morning, right? How did it go?"
Sengoku nodded but didn't offer a verbal reply. Instead, he simply willed his chakra outward.
In a seamless shimmer of displaced air, the boy vanished, replaced instantly by the towering, scarred figure of Sunada Shun. Sengoku swept his cold, dead eyes over the two older boys.
Tetsumaru and Matsufuji instinctively stiffened, their spines snapping straight. A flash of genuine unease crossed their faces. Even though they knew logically that it was just Sengoku, the sheer oppressive weight of Sunada's appearance and the flawless imitation of his icy glare made their skin crawl.
"Hey, hey, change back!" Tetsumaru waved his hands defensively, taking a step away. "That is seriously creeping me out."
Sengoku severed the chakra flow, returning to his normal appearance.
"Tch, what a monster..." Matsufuji muttered under his breath, though his unease quickly morphed into excitement. "That jutsu is incredibly handy, though! It's going to open up a whole new world for pranks."
Tetsumaru shook his head, rotating his wrists to loosen up. "Usual rules? Sparring first?"
Sengoku nodded. The moment the gesture was complete, his silhouette blurred.
Tetsumaru's vision swam. Before he could even raise his arms into a guard, a hand lightly chopped the side of his neck.
"Too fast—!" Matsufuji yelled, but the warning died in his throat. Sengoku appeared beside him like a ghost, executing a surgical leg sweep that ripped Matsufuji's balance out from under him.
Seeing an opening, Kakuda lunged from behind. But Sengoku merely sidestepped, shifting out of the attack's trajectory as if he had eyes in the back of his head, and lightly drove his elbow into Kakuda's exposed ribs.
The entire exchange lasted less than three breaths. All three upperclassmen were on the ground.
Matsufuji rubbed his bruised backside as he pushed himself up, looking utterly depressed. "We literally can't even touch you anymore."
Tetsumaru sighed, his chest heaving as he accepted the reality of the widening gap in their skills. Then, something clicked in his memory. "Ah, crap. The afternoon Ninja Tools class requires us to gather early to draw materials."
Realizing the time, the three seniors quickly packed up their gear and hurried out of the training ground.
Once the area was completely empty, Sengoku walked over to the edge of the clearing. Reaching into his ninja pouch, he retrieved a slightly worn scroll: Wind Release: Great Breakthrough.
He unrolled it, his eyes rapidly scanning the complex meridian pathway diagrams and the dense paragraphs of annotations.
Stepping into the center of the clearing, he closed his eyes to internalize the flow. For his first attempt, he drew a breath and exhaled. It produced nothing more than a scattered, disorganized breeze.
He frowned, making a mental adjustment to how his chakra gathered in his chest. On his second attempt, the airflow was slightly more concentrated, but still lacked any real kinetic force.
For the third try, he took a deep breath, rapidly condensing his chakra in his lungs, and expelled it violently.
Whoosh—!
A powerful shockwave of pressurized air erupted from his mouth, slamming aggressively into the sandy ground ahead. It carved a shallow, sweeping trench into the earth, throwing up a thick cloud of dust.
Sengoku let out a slow breath, assessing the drain on his reserves. "The control is too loose, and the chakra cost is too high," he muttered. He wasn't satisfied.
He glanced back at the scroll. The text detailed the jutsu's immense practical value: knocking back enemies, interrupting enemy hand seals, shattering defensive formations, and fueling allied Fire Release techniques. It was specifically noted to be devastating in narrow corridors and boasted a relatively low chakra cost, making it ideal for sustained combat.
His current version was anything but low-cost.
Keeping those tactical goals in mind, Sengoku fell into a rigorous rhythm. He repeatedly adjusted his breathing, refining the exact moment of chakra compression and release. Again and again, howling gales blasted from his mouth, swallowing the training ground in swirling sand.
Over the course of several days of high-intensity practice, the technique evolved. The wind pressure grew increasingly dense, and its effective range expanded significantly.
During this refinement process, Sengoku discovered a crucial mechanic about elemental ninjutsu. While bypassing hand seals entirely offered unparalleled surprise value, it came at a severe cost: elemental chakra was inherently volatile. Forcing it to take shape purely through willpower caused massive energy bleed and severely capped the jutsu's maximum destructive power.
However, if he supplemented the technique with a simple, guiding hand seal—specifically the Ram or Dragon seal—it acted as a mechanical focal point. The seal effortlessly organized the chaotic wind chakra, drastically cutting down unnecessary drain while concentrating the blast into a much heavier, more violent impact.
Now, several days later, Sengoku stood before a waist-high, heavily weathered boulder.
His hands blurred, snapping into a simplified Dragon seal against his chest. He drew in a breath, his lungs burning with hyper-compressed wind chakra, and exhaled.
Boom!
The condensed gale struck the rock face like a physical sledgehammer. The heavy, muffled impact echoed across the training ground. The boulder shuddered violently, and a web of fine, spider-silk cracks spread across its surface as pulverized stone rained down.
Sengoku lowered his hands, nodding in satisfaction. Incorporating the seal had perfectly optimized the jutsu's efficiency and lethality.
He cut off the lingering flow of chakra. His eyes shifted away from the cracked boulder, landing on a second scroll waiting nearby.
'Wind Release: Wind Cutter.'