Seeing how cooperative Kakashi was, Shin Uchiha nodded in satisfaction. One reason he had left this Mangekyō Sharingan with Kakashi was to see whether discovering its Dōjutsu, Kamui, several years early would allow Kakashi to uncover Obito Uchiha, who was hiding behind the scenes.
Another reason was that, since he could not find Obito Uchiha for now, he could have Kakashi use Kamui whenever they had some free time and toss a few ninjutsu inside for fun. The chances of hitting Obito Uchiha by coincidence were slim, but it was like opening a mystery box. Wasn't that exciting?
Shin Uchiha gave Kakashi a final reminder. "With this Sharingan of yours, I've already guided you through using it and let you feel how to evolve it into a Mangekyō Sharingan. Remember that feeling and work toward it. Once you can activate it through your own efforts, your powers of observation and your genjutsu abilities will both receive a tremendous boost.
"Also, if you paid close attention to what you felt earlier, you should have noticed a special power within this Mangekyō Sharingan, something that is neither ninjutsu nor a secret technique. That power is the Dōjutsu unique to our Uchiha Clan's Mangekyō Sharingan."
Shin Uchiha paused. Seeing Kakashi nod to indicate that he had felt it, he continued, "This Dōjutsu is another power unique to our Uchiha Clan's Mangekyō Sharingan. It varies from person to person; everyone's is different. Once you can activate the Mangekyō Sharingan, take the time to feel it carefully. It will tell you what it does."
Shin Uchiha went over a few more precautions with Kakashi. As someone who possessed the Uchiha Clan's legacy, he naturally knew far more than Kakashi, a Sharingan novice. Knocking Kakashi unconscious and copying his Dōjutsu, Kamui, had yielded a great reward,