Naruto: Chakra System

Sasuke was startled by this information from Kakashi; he stood up immediately, his expression full of disbelief and anger. Kakashi smiled, looking at Sasuke's expression.

"Before you think anything else," he said, "I'll tell you it's not any secret and nothing like you think that it was forcefully taken or something."

Sasuke was not convinced, looking at Kakashi with mixed expressions. Naruto and Sakura were also surprised but didn't speak, letting Kakashi talk.

Kakashi stated, "This was the eye of my teammate, who belongs to your clan, Obito Uchiha. He gifted me this eye before his supposed death. My other teammate, Rin Nohara, took this eye out and, with Mystic Palm Jutsu, transplanted it into my left eye socket."

Sasuke was still a little enraged, but hearing this, he felt a little convinced. However, the thought that the Dōjutsu of his clan, which was their pride, was in someone else's eye was still inconviencable for him.

Naruto asked like he understood everything, "Oh, so that's why you hide it, so any enemy ninja wouldn't know about it!"

Kakashi looked at Naruto with a blank expression. "Your ears are really clogged," he said. "Didn't I just say that this thing isn't any secret? You three or other Genin didn't know anything about me during academy time, because these kinds of things aren't taught in the ninja academy, but I told you before that I am one of the feared ninja in other nations. Many even know me as 'Kakashi of the Sharingan' and 'Copy Ninja Kakashi'."

Naruto chuckles embarassingly, scratching his head, and they all nodded, but only Sakura thought that Kakashi still hadn't answered why he covered his left eye. She asked, "But Sensei, what exact reason is it that you have to cover it, if it's not any secret?"

Sasuke was dumbfounded for a moment; he himself hadn't thought about it and looked at Kakashi intently. Sasuke has got this information in the anime during the Land of Waves mission arc, and questioned that is Kakashi from Uchiha Clan? But current circumstances were different, so Sasuke's reaction was also different.

Kakashi replied, "Because I am not Uchiha, so I can't deactivate the Sharingan, and it continuously drains my chakra."

Sakura and Naruto asked, "Continuously drain chakra?" Sasuke, however, understood; he also felt that once he activated his Sharingan, it consumed his chakra, though not much.

"Yeah, I can't deactivate it, so it always stays in an activated state, which is quite chakra-consuming," Kakashi said. "Even now, when my left eye is covered and closed, it's still draining my chakra."

They were surprised. Naruto asked, "Even then you don't ever look exhausted, Sensei, if it's really draining your chakra all the time!"

Kakashi waved his hands casually. "My chakra reserves are good, so it's not a problem," he said. "Moreover, thanks to it, I was able to copy many Ninjutsu, Genjutsu, and techniques."

Sakura thought and asked, "Does that mean Sasuke-kun can also copy Ninjutsu?"

Naruto made faces at hearing this; he also wanted to learn how Kakashi could copy Jutsu, but hearing it was because of the Sharingan, he understood he couldn't do that as easily as he initially thought he could.

Sasuke also asked, "Can I really copy Jutsu?"

Kakashi nodded. "You can, but at your current stage, with One-Tomoe, it's difficult to copy Jutsu," he said. "Though you can, but only low-rank ones. Once you reach the Three-Tomoe stage, you can copy Jutsu much more effectively."

Sasuke nodded and asked curiously, "Does that means your teammate, whose Sharingan you have, had it evolved to the Three-Tomoe when it was given?"

Kakashi's eye showed a mischievous glint because he knew the answer he would give would completely shock Sasuke.

Kakashi shook his head. "Nope, it was at the Two-Tomoe stage," he said. "Later, I evolved it to the next stage. Moreover, Obito directly awakened his Sharingan at the Two-Tomoe stage."

Sasuke was stunned, disbelieving and bewildered. After seeing his clan annihilated by his own brother, even his parents killed, he only awakened One-Tomoe.

Though Sasuke never felt much low about it, because from what he knew, usually any Uchiha awakened Sharingan at One-Tomoe, and later stages were difficult to evolve. And here he was hearing that one Uchiha Clansman awakened it directly at Two-Tomoe, and a non-Uchiha even evolved it to the next stage.

Though that wasn't completely true, Kakashi didn't evolve it. Obito's Two-Tomoe Sharingan had directly transformed into Mangekyō Sharingan, so Kakashi's eye also evolved.

But no one actually knew, and many even from the Uchiha Clan back then believed that it was Kakashi who evolved it to the next stage, which was kind of a hard slap on many's faces, especially those who opposed Kakashi having the Sharingan, saying only the Uchiha Clan could use it to its full potential, not any non-Uchiha, so they can't tolerate Sharingan going out from Uchiha Clan.

But amidst Sasuke's bewilderment and Naruto's slight jealousy that he couldn't copy Ninjutsu like Sasuke would in the future, Sakura asked a question, "Kakashi-sensei, why is it that your Sharingan is always in an activated state?"

Kakashi glanced at Sakura, thinking what a stupid question that was, and simply said, "Didn't I already tell you that non-Uchiha can't activate and deactivate it at will? That's why."

Sakura shook her head and clarified, "That's not what I mean. I mean, if that eye was taken out of your teammate's socket, then shouldn't it be in a deactivated state, and even if it's transplanted into your eye, it should be in a deactivated state all the time, since you can't activate or deactivate it at will? So why is it always on activate? I mean, it should be in a deactivated state when it's taken out and transplanted, right?"

Kakashi's visible eye widened and thought, 'Whoa, that's quite a creative question she asked here, really.'