Instructor Sunada Hayato wasted no time on pleasantries. His hands blurred in front of his chest, weaving the four basic seals—Ram, Boar, Horse, Tiger—in a single, flawless sequence.
"Watch closely."
Before the last syllable faded, the space where he stood was abruptly replaced by a scarred wooden log. Hayato instantly reappeared several meters away. The entire transition produced nothing but a soft whoosh of displaced air.
Hayato walked back to his original spot and kicked the log aside. It hit the dirt with a dull thud. "Weave the seals, channel your chakra, and instantly swap places with a pre-marked object," his voice grated, hard as weathered stone. "We typically use specially treated wooden logs because they easily retain chakra signatures. The core of this technique is chakra mobilization and spatial perception. Miscalculate by even a fraction, and you die."
He crouched, tracing his rough fingers over the faint formula carved into the wood, before standing up and raising a stern finger.
"Memorize these rules. Your lives depend on them."
"One: The formula must be re-bound before every single use. These logs are consumables. Do not use the same one endlessly; every swap degrades its structural and energetic integrity."
"Two: The chakra bound to the log dissipates over time. If it runs dry and you try to swap, you're just signing your own death warrant."
"Three: Distance limits. Do not stray too far from your marked target. The further you are, the greater the spatial deviation. Push it too far, and the jutsu simply fails. The optimal range depends on your sensory capabilities. Some can swap over long distances, while others are capped at ten meters. But no matter how talented you are, this basic jutsu cannot exceed a hundred-meter radius."
"Four: Never use this in front of a sensory ninja. They will track the spatial chakra fluctuation and predict your exact reappearance point. You won't be dodging an attack; you'll be teleporting directly into their blade."
"Five: Do not spam this technique. Rapid, successive use will cause irreversible tearing to your chakra meridians. During today's practice, everyone is mandated to take a full one-minute rest to regulate their coils between each attempt."
"Six: The most critical rule." His voice dropped to a lethal chill. "In absolute emergencies, you can substitute the log for other nearby objects, but remember this: never attempt a swap without binding a formula first. This jutsu is fundamentally a rudimentary reverse-summoning technique. Without a marked anchor to lock onto your coordinates, you aren't teleporting safely. If you're lucky, the jutsu simply fails. If you make a mistake, the chakra backlash will tear you into spatial turbulence, and you will be ripped apart."
"Now, inspect your formulas and begin. Now!"
The students scrambled to grab their training logs. Sengoku picked his up, his sensitive fingers tracing the wood. He could clearly feel the faint chakra anchor embedded within. Hayato's lecture had perfectly mapped out the resonance nodes required to link the hand seals to the formula, and Sengoku absorbed the theory instantly.
He stepped into an open clearing, placed his marked log on the ground, and wove the seals. The moment the sequence finished, his internal chakra violently resonated with the anchor in the wood.
Poof!
His vision blurred. After a split-second sensation of weightlessness, Sengoku found himself standing exactly where the log had been. A perfect swap.
Following orders, he rested for sixty seconds to let his meridians cool before trying again. His second attempt was even smoother. He began to clearly understand the underlying mechanics—it wasn't physical movement, but a direct swap of spatial coordinates.
'An E-rank difficulty... but it touches on reverse summoning?' Sengoku suppressed his inner shock and continued the drills.
His hand seals approached near-instantaneous speeds, and his swaps were flawlessly precise. But the limitations of the jutsu were glaring. After twenty minutes of practice, the log was already developing hairline fractures, and a significant portion of his chakra was drained.
Sengoku turned his attention to a discarded block of sandstone near the edge of the field, roughly his size. Rock was a notoriously poor chakra conductor compared to treated wood; the resistance was massive. He focused his mind, forcibly driving a dense spike of chakra into the stone to establish a crude anchor.
He stepped back and wove the seals.
Poof!
The swap succeeded, but the moment he reappeared, he stumbled, violently thrown off balance. He had missed his mark by nearly three meters.
Sengoku steadied himself, his brow furrowed in thought. Non-standard objects were incredibly difficult to mark, the sensory connection was muddy, and the resulting swap was wildly unstable. In a life-or-death battle, a three-meter deviation was fatal. Furthermore, the sheer number of restrictions on the Body Replacement Jutsu made it highly situational. For standard evasive maneuvers, his high-speed Body Flicker (Shunshin) was vastly superior.
Then there was the issue of mass. Standard logs were huge; carrying more than two or three into battle would cripple his mobility. And since they required pre-binding and couldn't be used continuously, the jutsu felt riddled with tactical flaws.
'If the essence of the jutsu is coordinate replacement, does the anchor actually need to be a solid object of similar mass?' His mind raced. 'Could it be smaller? A single wire? A grain of sand?'
He immediately discarded the idea. Even with his massively upgraded intelligence and chakra control, he couldn't possibly etch a stable spatial formula onto something that microscopic. And even if he could, how long would the chakra last? Microseconds, at best, before it dissipated. That level of effortless, instantaneous spatial swapping belonged exclusively to god-tier abilities like the Flying Thunder God or Amenotejikara.
Since microscopic objects were out of the question, what about preparing an object with a lethal secondary function? Like *The Pursuer*?
The tactical blueprint suddenly crystallized in his mind. He could pre-place the iron puppet on the battlefield. The moment an enemy closed in for a fatal strike, he would trigger the substitution. He would instantly teleport to safety, while the enemy's blade would strike a rigged, pressurized iron bomb left in his place.
It was an offensive evasion. Compared to the primitive tactic of slapping an explosive tag onto a log, swapping out with a fully armed, shrapnel-loaded puppet was infinitely more deceptive and devastating.
A cold gleam flashed in Sengoku's dark eyes. The theoretical foundation was sound, but realizing it required absolute mastery over the basics. He picked up a fresh training log, turning his back to the rest of the class, and threw himself back into the grueling, monotonous repetition.