Itachi lightly leaped and, just like in the original story, passed through the middle of the shuriken. However, as Sasuke pulled the shuriken back, one flew out and indeed struck Itachi's leg.
"This time it's finally not a genjutsu. Strange, how could Sasuke's eyes actually see through Itachi's genjutsu?" Black Zetsu exclaimed in disbelief.
"I'm not sure. It's possible Sasuke's eyes have surpassed Itachi," White Zetsu said, though his voice lacked much confidence. He was aware of many secrets. Clearly, he could discern that Itachi was deliberately losing, but of course, he wouldn't voice that.
"Fire Release - Great Fireball Jutsu." Seeing that he had hit Itachi, Sasuke felt elated and continued with determination. He expelled a massive fireball.
Although this battle was entirely one that Itachi had intentionally let himself lose, a battle he had choreographed and staged, he felt like he might have overdone it a bit. Added to that, he couldn't afford to be hit by that fireball, which was dangerous. He quickly leaped into the air to evade the Great Fireball Jutsu.
"You can't escape. Lightning Release - Chidori." Sasuke's eyes spun around, utilizing his insight to calculate Itachi's location. He immediately followed suit and jumped up, using Chidori to strike. However, Itachi dodged the Chidori again, and this time, it merely pierced through the rooftop.
"Fire Release - Great Fireball Jutsu." Itachi leaped even higher and emerged from the rooftop that the Chidori had punctured. He utilized the smoke to unleash the Great Fireball Jutsu, engulfing the smoke and flames together.
"Damn, is this still not enough?" As the smoke began to clear, Sasuke's form finally became visible. However, he activated the wings of his Level 2 Curse Mark of Heaven, blocking the Great Fireball Jutsu. He then promptly retracted the wings, returning to the first stage of the cursed mark. After all, the corrosiveness of the second stage was no joke. He was well aware that Orochimaru would try to seize his body once the battle was over or near its end.
His goal was to hold out, to kill Itachi while also activating the Mangekyo to suppress Orochimaru. After that, when his body had recovered, he would deal with Orochimaru completely. He couldn't afford any unnecessary wastage. Regrettably, he didn't know that he didn't need to do all of this. The moment he saw the cursed mark, Itachi knew that regardless of whether Sasuke killed Orochimaru or not, Orochimaru's soul was still within the seal.
It didn't matter who controlled Sasuke's body, whether it was Sasuke himself or Orochimaru. Itachi would seal Orochimaru before the battle ended. There was a good big brother, and this foolish little brother really didn't need to undertake any unnecessary actions.
"We almost got dragged into these two brothers' feud," Black Zetsu's head appeared from the other side of the rooftop. Apparently, they were both very interested in this battle. Regardless of whether Itachi intentionally lost or not, this battle was truly intriguing, especially when Itachi used the Mangekyo to teach his younger brother the use of the dōjutsu.
"Fire Release - Great Fireball Jutsu." Itachi and Sasuke suddenly formed seals and simultaneously unleashed the Great Fireball Jutsu. However, Sasuke had entered the first stage of the cursed mark, and he clearly had a stronger Great Fireball now. Itachi deliberately reduced the power of his own Great Fireball for this situation. He wanted Sasuke to take control.
After all, the strength of Fire Release wasn't solely determined by the quantity of chakra or the power of the user. What truly decided victory in Fire Release was the user's skill and the extent of their mastery over the technique. The amplification of Fire Release was a secondary factor, and the chakra quantity came last.
Considering Itachi's strength and mastery of Fire Release, his chakra quality would certainly not be lacking. While Sasuke had more chakra when in the first stage of the cursed mark, the quality of his chakra's improvement was only slightly inferior to or even slightly worse than Itachi's.
However, this was the outcome Itachi desired. The genjutsu he used earlier was Tsukuyomi, and now it was time to teach Sasuke to use Amaterasu.
"It seems like Sasuke has the upper hand now," Black Zetsu remarked.
"Probably. Sasuke has entered the cursed mark state, and while Itachi's chakra is relatively pure, the quantity is not sufficient. After all, he's not someone with abundant chakra. If the fight continues, even if Itachi's Fire Release is stronger, without enough chakra to sustain the burning of the fire, Itachi's Fire Release will fade, and Sasuke's Fire Release will prevail," White Zetsu nodded and explained.
"Amaterasu!" Itachi's right eye welled up with blood, and he suddenly opened it. The Mangekyo Sharingan was filled with bloodshot veins, and a spiraling Amaterasu flame manifested. No matter how many Great Fireball Jutsu Sasuke used, they were feeble before the Amaterasu flames. Within seconds, the Amaterasu flames completely devoured Sasuke's fire.
However, Itachi had no intention of using Amaterasu to kill Sasuke. If he wanted to kill Sasuke, he didn't need Amaterasu. He intended to teach his brother to use Amaterasu, not use it to kill him. So, the technique he used earlier wasn't Tsukuyomi on Sasuke but on the Great Fireball Jutsu. He closed his right eye as the Great Fireball Jutsu dissipated, as Amaterasu had also ended.
Sasuke widened his eyes. Although Amaterasu hadn't burned him, being so close, he still felt the terrifying power of Amaterasu.
Seeing that Itachi was about to open his eyes again, Sasuke didn't waste any time and immediately started running. He absolutely couldn't let Itachi's gaze focus on him, or he'd be in trouble. Believing he could dodge Amaterasu, Sasuke dashed away, just as Itachi wished, unleashing the Amaterasu flames.
"Wings!" As he saw that he was about to be engulfed by the Amaterasu flames, he immediately spread his wings, enveloping himself entirely. Then, he used Chidori to cut through the rooftop, and with a Body Replacement Jutsu, severed his own wings. Using his wings as the substitution, he combined it with Orochimaru's unique Body Replacement Jutsu, different from the standard version, to successfully evade the attack. In reality, this was just Itachi allowing Sasuke to dodge Amaterasu as he wished.
Otherwise, with the insight of the Mangekyo and Itachi's strength, how could Amaterasu only burn the wings? And how could Sasuke's Body Replacement Jutsu hide from Itachi's eyes? In truth, everything that happened earlier was a demonstration of the power and usage of Amaterasu for Sasuke, with some limitations. The main drawback was the substantial chakra consumption and the requirement to maintain visual focus on the target to be ignited.