"Did I really do wrong?" Itachi murmured to himself, his gaze vacant, as if he had lost all support in an instant.
"Come fight. Don't hold back." Sasuke's voice pulled him back to reality, his tone icy. "Only by killing you with all your strength can I slightly console those clansmen who died unjustly."
Itachi's lips twisted bitterly. "Is that so? I understand."
He took a deep breath, and the pattern of his Mangekyo spun instantly in his eyes.
"Tsukuyomi!"
He attempted to pull Sasuke into the world of Tsukuyomi. However, Sasuke merely looked at him calmly, not even activating his Sharingan. The moment Tsukuyomi's spiritual force touched Sasuke, it vanished without a trace, like a stone sinking into the sea. Even worse, the backlash caused Itachi to let out a muffled groan, a trail of bloody tears streaming from his eye.
"This level of Genjutsu," Sasuke's lips curled into an undisguised sneer, "isn't even worthy of my serious attention. Your capacity is too weak, Uchiha Itachi."
Itachi was puzzled, 'How had Sasuke managed this?'
He no longer hesitated and directly used his trump card.
Crimson Chakra erupted like a volcanic eruption, rapidly coalescing into a massive Susanoo, consisting only of an upper body skeleton. Though it was only in its initial stage, its terrifying defensive and offensive power was enough to make even Kage-level opponents stand on guard.
"Susanoo: Totsuka Sword!"
Itachi manipulated Susanoo, swinging the legendary spirit sword, carrying the force to seal all things, slashing towards Sasuke.
Facing this attack, capable of splitting mountains and seas, Sasuke still did not dodge. He simply raised his right hand slowly, clenching his five fingers into a fist.
"Pegasus Meteor Fist!"
The fist met the tip of the Totsuka Sword. A sharp crack rang out. Under Itachi's wide-eyed Mangekyo Sharingan gaze, his invincible Totsuka Sword, containing the power of sealing, began to crumble inch by inch from the tip.
Taking advantage of Itachi's shock, Sasuke threw another punch.
"Rozan Shoryuha!"
With this punch, Susanoo's arm and skeleton began to crack and disintegrate. In just two punches, the massive Susanoo completely dissipated like a sandcastle collapsing. Itachi fell from mid-air, a punch-hole clear through his chest.
Orochimaru, watching from afar, was speechless, 'Was this still a battle between Ninjas?'
Sasuke slowly withdrew his fist, looking at his brother whose life force was rapidly fading on the ground. There was no wild joy on his face from achieving revenge, only a cold indifference, as if his emotions themselves had frozen solid.
"What a... tasteless revenge," He muttered to himself.
Yet, the moment his voice fell, within the depths of his dark gray eyes, an eerie pattern quietly surfaced.
Under the impact of extreme hatred, contempt, and the complex emotions of finally ending it all with his own hands, his eyes had evolved on their own.
Setsuna's spiritual body emerged. He glanced at Sasuke's newly awakened Mangekyo, then at Itachi's corpse on the ground, and said calmly: "If you transplant Itachi's Mangekyo Sharingan now, your eyes will evolve into the Eternal Mangekyo Sharingan. You will gain greater Ocular Power and will never face the risk of blindness."
Sasuke did not wonder where his master had learned this. He was silent for a moment, then said decisively: "I don't want anything from him. I don't want to catch his stupidity."
Setsuna nodded. Indeed, in the original work, after Sasuke transplanted Itachi's eyes, his mental state became quite abnormal.
Sasuke looked at his own fists: "It's just a Mangekyo. At worst, I simply won't use it. I can defeat any enemy with just my own fists."
Setsuna smiled, 'Good, this was fitting for my disciple. What Legendary Eyes? I'll just give you two solid punches first.'
Setsuna looked at Sasuke and said: "Now that you have completed your revenge, come help me achieve my goal."
Sasuke snapped out of his detached state, looked at his master, and refocused his gaze: "What does Master want me to do?"
"Lend me your body... for a few minutes."
Sasuke did not hesitate. Without a shred of doubt, he nodded calmly: "Alright."
Setsuna's tone carried a hint of amusement: "Aren't you worried that, like Orochimaru, I want to take over your body?"
Hearing this, Sasuke laughed: "Master has already helped me achieve my greatest wish. Even if I gave my life to Master, what of it? Besides, I trust Master."
This unreserved trust caused even Setsuna's spiritual form to ripple slightly. He said no more, simply stating: "Then watch carefully how your master fights. This might be the last lesson I teach you in this world."
"Last lesson?" Sasuke's heart jolted. He asked hurriedly, "Is Master leaving?"
"Although this world is similar to mine, it does not belong to me after all." Setsuna's voice carried a hint of etherealness. "I'm also not sure... if I can come to this world again after this."
As his voice trailed off, Setsuna's spiritual body transformed into a stream of dark gold light and instantly vanished into Sasuke's brow.
Sasuke felt his consciousness pushed into the 'background', with control of his body temporarily transferred. But he could clearly see, hear, and feel everything his master did while controlling his body.
"Susanoo..."
A surge of Ocular Power, far surpassing what Itachi had displayed earlier, burst from Sasuke's eyes. A fully-formed Susanoo, hundreds of meters tall, clad in ancient armor and radiating the majesty of a deity, rose from the ground.
"Condense!"
With a soft command, the inconceivably massive fully-formed Susanoo rapidly shrank at a visible rate. Ultimately, it transformed into a layer of 'Susanoo' Tattoo shimmering with blue light.
Sasuke's consciousness watched this scene, stunned.
"I have extracted the 'Susanoo' residing in your Mangekyo and integrated it into your Tattoo. From now on, you can freely utilize Susanoo's defensive and some offensive characteristics without consuming Ocular Power or worrying about blindness."
For Setsuna, who had achieved the Eighth Sense and whose soul had transcended its limits twice, achieving this was not difficult. He was not merely akin to a deity... with his level of attainment, he was a true deity in the worlds of Saint Seiya and Bleach.
Sasuke's consciousness was overwhelmed with shock: "Master can even do something like this, directly 'solidifying' the ultimate secret art of a Kekkei Genkai into a constant state?"
Although he had long known his master was powerful as a god, every time he witnessed his master act, he was still awed by his strength.
Having accomplished this, 'Sasuke' looked up at the sky and slowly clenched his right fist.
"Watch closely. Space is not an insurmountable barrier."
The moment his voice fell, he threw a simple punch at the void before him.
Crack!
A terrifying sound, as if the world's glass pane had shattered, shook the soul. Space tore apart, revealing the violent, chaotic space-time currents beyond.
Setsuna, controlling Sasuke's body, calmly stepped inside.