Naruto naturally knew who the man Sasuke was talking about was—Itachi Uchiha, Sasuke's older brother, and the mastermind who had personally sent the Uchiha clan to hell.
Itachi Uchiha had always been Sasuke's nightmare.
For all these years, Sasuke had worked so hard not to avoid getting beaten up by Naruto, but to kill Itachi Uchiha and avenge his father, his mother, and every member of the Uchiha clan.
Naruto knew all about Sasuke's pain.
If Sasuke had not had the care of friends like them, Naruto did not know how deeply the pain of that massacre would have affected Sasuke, or what kind of future Sasuke would have walked into because of it.
Naruto had once promised Sasuke that they were friends and would face anything together. So he hurriedly comforted the somewhat anxious Sasuke. "Sasuke, don't panic. Take it slow. Where is Itachi Uchiha?"
Naruto's words had always worked on Sasuke. Sasuke immediately forced himself to calm down and said, "Naruto, I've been restless all day. I keep thinking about that incident, and his figure keeps flashing through my mind. I have a feeling that he'll definitely come to Konoha today."
So it had all been Sasuke's intuition... Naruto looked at Sasuke and said, "Sasuke, don't panic. Haven't you already prepared for how to deal with him? If he dares come to Konoha, I'll smash him to pieces with you."
Seeing his good friend Naruto firmly standing by his side as always, Sasuke was moved. Then he said resolutely, "Itachi Uchiha must die."
Itachi Uchiha must die!
Sasuke had wandered in confusion for a long time before making that decision. Though making it caused him great pain. After all, Itachi Uchiha had given Sasuke so many beautiful memories, so much love.
How could Sasuke not suffer when he