Tobirama had actually developed the Flying Thunder God technique several months ago but had kept it hidden, intending to use it as a secret weapon to find an opportunity to seize the Uchiha by the throat for a fatal blow.
Taihang Mountain had been an impenetrable barrier for the Uchiha for centuries. But this had also made them overconfident, causing them to move too many of their forces to the front lines and leave the defenses here weak.
An ordinary ninja, even a Kage-level one, could never have bypassed so many people on the front lines to sneak into Taihang Mountain right under the Uchiha's noses. But Senju Tobirama, a sensor-type ninja armed with the Flying Thunder God, could. He was a naturally gifted sensor, even surpassing Hashirama in this regard, able to perceive the entire situation on a battlefield. At his peak, he could even sense the exact number of enemy combatants at once.
With a one-man surprise attack, he had miraculously shattered the Uchiha's last line of defense led by Uchiha Sen. He was just about to take the location and then coordinate a pincer attack with Senju Yuma and his brother Hashirama on the front lines. If he had succeeded, the Uchiha, even if not wiped out, would have suffered a devastating blow, losing their ability to contend with the Senju.
But Izuna's sudden arrival had caught him completely off guard.
Uchiha Sen was equally shocked by Izuna's appearance. "Young Lord Izuna, weren't you on the front lines?" he shouted.
"Uncle Sen, fall back. Administer first aid to any clansmen who are still breathing," Izuna said, leaping down from the lookout tower.
Uchiha Sen was of the same generation as Uchiha Tajima, so Izuna naturally addressed him as such.
Wiping the blood from his forehead, Uchiha Sen helped two injured but still conscious Uchiha jonin to their feet. "Be careful. That kid's techniques are wickedly strange."
Uchiha Sen's skill was originally on par with Tobirama's, and he was even more experienced. But the Flying Thunder God was simply a broken jutsu, capable of killing opponents of a higher level.
"A slight complication, but no matter." Tobirama recovered from his shock, his poker face returning. He drew a new Flying Thunder God kunai. "After I capture you, you'll serve as a fine bargaining chip in negotiations with the Uchiha."
The two had fought many times before. Tobirama knew Izuna's strength and was confident that with the Flying Thunder God, he could not lose.
"Hmph. Big words," Izuna responded coldly. The three tomoe in his eyes spun rapidly, transforming into a new shape resembling three vertical prongs.
*A Sharingan I've never seen before?!* Tobirama was momentarily startled.
But it didn't make him panic. He formed a one-handed seal, and in the next second, a tsunami-like wave of water over twenty meters high erupted from behind him.
Water Release: Water Shockwave!
The skill level of ninja in the Warring States period far surpassed that of later generations. A genin from this era was almost stronger than a chunin from Naruto's time.
"Fire Release: Great Fire Annihilation!"
Izuna brought his hands together, took a shallow breath, and unleashed a super-scale fire jutsu from his mouth with a range that rivaled Tobirama's water attack.
*WHOOSH!*
As fire and water collided, a massive cloud of steam and a powerful shockwave sent the tents of the Uchiha camp and the bodies of some clansmen flying.
*A pity. The eyes of these clansmen could still be recovered and used, but eye transplant techniques seem to be underdeveloped in this era...* Izuna thought grimly. It was a dark practice, but all too common in the Warring States.
Suddenly, Tobirama's presence vanished.
Less than a second later, he appeared about ten meters directly above Izuna. The clash of their high-level jutsu had scattered the Flying Thunder God kunai Tobirama had planted around, and one of them had been flung into the air right above Izuna's head. Tobirama seized the chance to teleport there.
"Got you!" Tobirama shouted.
However, he was unaware that in the instant he vanished, the Mangekyo Sharingan in Izuna's left eye, hidden beneath his bangs, was spinning madly, generating a scene like a movie—
*In the vision, Tobirama disappears with the Flying Thunder God, then teleports above me, attacking my head with a seal-less water jutsu, Heavenly Weeping.*
Sure enough, as the vision faded, the real Tobirama above Izuna spat a shower of water needles down at him.
"Water Release: Heavenly Weeping!"
Izuna pulled a scroll from the ninja tool pouch on his thigh. With a press of his palm, countless kunai and shuriken shot out, connected by wires almost invisible to the naked eye.
In an instant, with the threads held in his mouth and hands, Izuna whipped them upwards.
*SHING! SHING! SHING!*
The kunai and water needles collided, creating a fierce symphony of clashing metal before dissolving into spray and shrapnel in mid-air.
"Uchiha Shuriken Jutsu?" Tobirama's pupils contracted. But what surprised him even more was that Izuna had completely seen through his attack trajectory.
*How is that possible?! This should be the first time he's seen my Flying Thunder God!*
Suddenly, Tobirama's vision blurred. From within the shuriken shrapnel that should have been obliterated along with his water jutsu, new shuriken inexplicably appeared. The central holes were threaded with wires, which swung them in a wide arc toward his flank.
Shuriken hidden within shuriken!
This was the Uchiha's Shadow Shuriken Technique!
Tobirama refused to believe it and vanished from mid-air again. It wasn't a Body Flicker; it was the Flying Thunder God. His special kunai were now scattered all over the battlefield. Even the predictive abilities of the Sharingan couldn't possibly anticipate which kunai he would appear at.
Perhaps Tobirama had developed the Flying Thunder God specifically to counter the Sharingan's precognition.
However, in Izuna's spinning left Mangekyo, the movie-like vision played out once more—
*Tobirama appears at the nine o'clock position, next to a Flying Thunder God kunai stuck in a broken tree, and attacks me at high speed with the advanced water jutsu, Water Severing Wave.*
The vision receded. Izuna looked toward the nine o'clock position. About two hundred meters away, on a snapped tree trunk, a Flying Thunder God kunai was indeed embedded.
Before Tobirama could even appear, Izuna was already moving.
He dashed toward the broken tree, a swirling azure sphere the size of two fists materializing in his right hand. It was surrounded by four blade-like protrusions of wind and emitted a sharp cutting sound.
Wind Release: Rasengan!
He hadn't awakened Sage Chakra, so he couldn't throw it yet, but it was still an A-rank advanced wind jutsu!
As Izuna charged, Tobirama teleported to the tree. He was just about to form a one-handed seal to launch his "Water Release: Water Severing Wave," when Izuna's Rasengan was already smashing toward his face!
"What?!"
Surprised, Tobirama relied on his years of battle experience to barely twist his head aside, but the Rasengan still grazed his cheek and shoulder.
*SLASH!*
Blood sprayed from his cheek and shoulder. Most of the force of Izuna's Rasengan had missed.
After being injured, Tobirama immediately used the Flying Thunder God again, disappearing and reappearing five hundred meters to Izuna's right rear, where another of his kunai had landed.
*BOOM!*
Izuna's Rasengan pulverized the spot where Tobirama had been. A few seconds later, Izuna emerged from the billowing smoke, frowning. "Flying Thunder God... What a troublesome jutsu."
Tobirama's feelings were even more complicated. *Why? The Sharingan's predictive abilities shouldn't be able to foresee the Flying Thunder God! Is it the ability of that new Sharingan?*