Sasuke Uchiha, who was Tsunade, possessed immense power in every Isshiki.
This made Uchiha Itachi completely hesitant to take his punches head-on, and instead used his agile movements to fight his younger brother.
Sasuke's body also has Lightning Release Chakra stimulating cells, which increases his speed.
However, it was clear to Shinsei that his combat experience was far inferior to that of Uchiha Itachi.
Each time, Uchiha Itachi dodged Sasuke's punch by the narrowest of margins, but those very margins seemed like an insurmountable chasm that Sasuke could never overcome, which made Sasuke increasingly impatient.
Uchiha Itachi's Hand Seals with lightning speed, and in the blink of an eye, a fireball shot out of his mouth and hurtled towards Sasuke.
Sasuke neither dodged nor evaded, his entire body enveloped in Lightning Release Chakra, as he raised his fist and smashed it towards the oncoming fireball.
With a deafening roar, the fireball exploded, bursting into flames.
Sasuke Uchiha's body burst out of the flames and continued to smash towards Uchiha Itachi.
Seeing the huge opening in Sasuke's chest, Uchiha Itachi extended his right leg and kicked him squarely in the chest.
But the attack had no effect; Sasuke's body was like a huge, charging beast, and his right leg was completely useless.
He had no choice but to use the momentum to push off, flip in the air, and land steadily on the ground.
Uchiha Itachi continued to Hand Seals, spewing out several fireballs mixed with Shuriken, blocking all of Sasuke's paths in all directions.
Sasuke quickly extended two fingers, and a blue Chakra sword materialized in his hand, swiftly slashing at the oncoming Shuriken.
With two clangs, the Shuriken were sliced in two by Sasuke's Lightning Sword and stuck into the surrounding walls.
In a sense, Sasuke's fighting style was learned from Shinsei.
Because they often sparred together, Sasuke never hesitated to activate his Sharingan and copy the Taijutsu of opponents stronger than himself. Among them, Shinsei's fighting style was more suitable for him with his Sharingan.
With the same swift movements, the same Chakra Enhanced Strength Technique, and even having learned Shinsei's Ninjutsu Without Hand Seals, Lightning Sword, this fighting style made Uchiha Itachi extremely troublesome.
Sasuke Uchiha also possesses the Mangekyō Sharingan, so ordinary Genjutsu is completely ineffective against him.
Shinsei also realized that Uchiha Itachi wasn't as powerful as he had imagined. He had initially thought Uchiha Itachi would hold back relentlessly in the fight between his brothers, but now it seemed there was no need for that.
But thinking about it, it makes sense. The current Sasuke possesses Hashirama Cells, Tsunade's Superhuman Strength, Shinsei's Ninjutsu Without Hand Seals, and a pair of Mangekyou Mangekyō Sharingan. In every aspect, he is stronger than the Sasuke from Shippuden in the original work.
As for Uchiha Itachi, for some reason, his body seemed extremely weak.
According to the timeline, he should still have two or three years left. I don't know what happened that made him so eager to challenge his younger brother to a duel.
Uchiha Itachi's use of Fire Style was exceptional; ordinary Fire Style in his hands were practically works of art.
Using the shockwaves generated by the Fire Style explosions, he repeatedly Sasuke's swift movements away. The Uchiha Shuriken Manipulation Technique in his hands was like an obedient arm, always able to cut off Sasuke's attacks from unexpected corners.
However, Sasuke was no less formidable. His long Chakra sword was practically unstoppable, easily slicing through Lightning Sword, from steel wires to Shuriken flying from the opposite side.
"Cough, cough," Uchiha Itachi covered his mouth, blood seeping from it. He looked at Sasuke, a smile on his face, "It seems you've truly grown, my foolish little brother. Then let me show you the true power of the Uchiha."
Red Chakra surged rapidly from Uchiha Itachi's body, quickly forming a giant skull.
Muscles and veins grew from the skeleton's bones, and a new layer of skin covered it. The red, half-giant enveloped Uchiha Itachi, holding a Chakra sword in one hand and a shield in the other. The enormous half-giant Chakra body almost reached the ceiling of the hall.
"My foolish brother, this is the ultimate power of the Uchiha Clan — Susanoo!"
Sasuke snorted coldly, purple Chakra surging from his body, quickly forming a half-body Chakra giant. He held a giant crossbow in his hand and aimed it at Uchiha Itachi opposite him.
"Cough, cough! You've actually developed those eyes to this extent? You must have used their power quite a bit."
Uchiha Itachi covered his mouth, his voice trembling, "Can you feel the change in your eyes? The one who awakens these Mangekyō will eventually lose their sight. Only by plundering your brother's eyes can you possess the eternal Mangekyō! My foolish brother, quickly offer up your eyes!"
"Eyes, eyes! You never stop talking about these eyes! For these eyes, you killed your parents, you killed your entire clan! Uchiha Itachi! I will kill you! I will place your head before your parents' gravestone!"
"My foolish brother, come on! Use all your power! Otherwise, I'll take your eyes and use the power of the Eternal Mangekyō Sharingan to kill your friends!"
"Cough cough!" This cough came from Shinsei's mouth. He quickly covered his mouth and stopped making any sound.
The main point is to criticize Uchiha Itachi; with his Eternal Mangekyō Sharingan, he couldn't have killed his current self.
Unless one gains control of another Nine-Tails like Madara Uchiha, one cannot defeat oneself.
Sasuke's face twisted into a grimace. With a thought, his Susanoo raised a giant crossbow and aimed it at Uchiha Itachi. A purple Chakra arrow hurtled toward Uchiha Itachi at lightning speed.
The red Chakra giant held up its Chakra shield in front of it.
With a deafening roar, a massive shockwave erupted from the shield, the violent explosion causing a painful strain on the ears of everyone present. Countless specks of dust and debris continued to fall from the roof.
Shinsei clasped his hands together, and a huge wall of water rose from the ground, blocking him and Kisame inside. Kisame stared at Shinsei's palms, seemingly mesmerized.
Noticing Kisame's gaze, Shinsei turned his head and asked in a low voice, "What's wrong, Mr. Kisame?"
"It's nothing." Kisame turned his face away and continued watching the fight between the two brothers in the arena.
Shinsei didn't notice that Kisame had also clasped his hands together inside his wide sleeves. As he activated his Chakra, nothing changed.
He kept a straight face, pretending to be nonchalant, but he had already secretly made up his mind that he must learn a hand Ninjutsu Without Hand Seals when he got back.
"My foolish brother, it seems your Susanoo still a bit unfamiliar."
The red Chakra giant swung its longsword and slashed powerfully at the purple Chakra giant opposite it!