No need for further questions. This fact alone was enough for Uchiha Shinji to confirm that the fully damaged Mangekyo Sharingan in Karin's eye sockets had truly been completely restored.
"I have to say, your constitution is even more extraordinary than I imagined!"
Shinji let out a sigh of admiration.
He had already overestimated Karin as much as he could, but the results she delivered still surprised and delighted him!
Karin hurriedly asked, "Leader, I didn't disappoint you, did I?"
"Your performance was exceptional!" After giving his affirmation, Shinji's joy faded, and he asked seriously, "Since you've activated this pair of Mangekyo Sharingan on your own, you must have mastered the dojutsu contained within them, right?"
Karin nodded eagerly. "Yes, yes! The left eye holds a dojutsu called Amaterasu, and the right eye contains one called Kagutsuchi. The left eye's Amaterasu can unleash black flames, while the right eye's Kagutsuchi can shape those black flames."
Halfway through her explanation, Shinji froze, muttering to himself, Wait, wait… aren't those the two dojutsu of Sasuke's Mangekyo?
He was no stranger to either Amaterasu or Kagutsuchi.
Amaterasu needed no introduction.
As for Kagutsuchi, in the original timeline, it was the dojutsu awakened in Sasuke's right eye after he unlocked his Mangekyo Sharingan!
"How could they be exactly the same?"
Shinji was puzzled.
But on second thought, Uchiha Fugaku, Uchiha Itachi, and Uchiha Sasuke—all from the same lineage—had each awakened Amaterasu upon unlocking their Mangekyo Sharingan.
Clearly, it wasn't impossible for different Mangekyo Sharingan to awaken the same dojutsu.
"Could the fully damaged Mangekyo Sharingan Karin restored belong to an ancestor of Sasuke's line? Wait, I remember during the Fourth War, when the Second Hokage saw Sasuke use Kagutsuchi, he didn't seem surprised at all and even made a few casual remarks about it."
All three—Sasuke, his father, and his brother—had awakened Amaterasu, suggesting their lineage had a high probability of awakening it.
From this, it was reasonable to deduce that the fully damaged Mangekyo Sharingan Karin restored likely belonged to one of Sasuke's ancestors.
After all, if Sasuke's lineage didn't have prominent figures in its past, their branch wouldn't have secured the position of Uchiha clan leader.
Moreover, during the Fourth Shinobi War in the original timeline, the Second Hokage's comments on Sasuke's Kagutsuchi clearly indicated he had seen—and perhaps even studied—the dojutsu before.
Kagutsuchi was merely an ability to shape Amaterasu's flames, and awakening Kagutsuchi alone would be meaningless. Logically, Kagutsuchi would always awaken alongside Amaterasu.
In other words, during the Second Hokage's era, there had existed a pair of Mangekyo Sharingan that simultaneously possessed Amaterasu and Kagutsuchi.
Shinji had always assumed this person was Uchiha Madara's brother, Uchiha Izuna, but now it seemed there might be another candidate.
"Wait, it's also possible Sasuke's lineage descends directly from Uchiha Izuna."
Shinji recalled that when Uchiha Madara met Sasuke, he remarked that Sasuke strongly resembled his brother, Izuna.
Uchiha Izuna's Mangekyo Sharingan had been fused by Madara to form an Eternal Mangekyo Sharingan, but that didn't mean Izuna had no descendants.
Perhaps the Uchiha who later chose to betray Madara and remain in the village was Izuna's heir—the ancestor of Sasuke's lineage.
This person ultimately defeated and subdued several ambitious Uchiha who, in Madara's absence, recklessly used Izanagi to vie for clan leadership. By stabilizing the Uchiha clan and restoring order, their lineage secured the clan leader position, and their Mangekyo Sharingan were passed down.
Seeing Shinji lost in thought, Karin cautiously asked, "Leader, what's wrong?"
"Nothing."
Shinji quickly dismissed his speculations.
The original owner of the fully damaged Mangekyo Sharingan Karin restored was, at this point, irrelevant.
The fact that Karin could freely activate and deactivate this pair of Mangekyo Sharingan and master their two dojutsu proved Shinji's earlier hypothesis correct!
By reviving this pair of Mangekyo that had completely lost their dojutsu power, Karin had usurped the original owner's authority.
In other words, Karin was now the true owner of this Mangekyo Sharingan!
This was the prerequisite for advancing toward an Eternal Mangekyo Sharingan, as only one's own eyes could evolve further.
"Finally, we've reached this step!"
Suppressing his excitement, Shinji retrieved the nutrient canister containing the Mangekyo Sharingan imbued with the dojutsuSusanoo Tomoshibi.
Karin stared at the familiar pair of Mangekyo in the canister and asked, "Leader, are we starting now?"
"Yes, time is tight. We need to seize every second!" Nodding, Shinji continued, "Prepare yourself. I'm about to begin the fusion surgery."
"Yes!"
Karin obediently lay on the bed, quietly awaiting the procedure.
Shinji began preparing the surgical instruments.
The success of this fusion hinged on the degree of rejection between the two pairs of Mangekyo Sharingan. If the rejection was severe, the fusion would likely fail.
This was why only Mangekyo from close blood relatives could fuse to form an Eternal Mangekyo Sharingan!
Karin's case was unique.
The Mangekyo Sharingan in her eyes had fully recognized her as their master.
The other pair of Mangekyo Sharingan, which Shinji planned to fuse with them, had been partially damaged and restored through Karin's body, making them highly compatible with her as well.
Thus, despite Karin not being an Uchiha and the two pairs of Mangekyo lacking close blood ties, Shinji's method of restoring them through Karin's body had created the possibility of fusing them into a single Eternal Mangekyo Sharingan!
Moreover, to ensure the fusion's success, Shinji had adapted Tsunade's fusion agent formula to create a simplified version.
While this simplified fusion agent might not counter rejection as severe as that of the First Hokage's cells, it should have no trouble mitigating rejection between the two pairs of Mangekyo Sharingan.
With everything ready, Shinji stood by Karin's bedside. "The fusion surgery is about to begin. Anything you want to say?"
Karin gently shook her head. "Please begin. I'm ready!"
Shinji smiled faintly. "Relax. For you, this won't be difficult."
The Leader's approval meant more than anything. Karin's spirits soared. "Yes, I won't let you down!"
Without further words, Shinji began the fusion surgery.