Do you mean Itachi Uchiha? He first appears in Naruto: Shippuden in person in episode 12 and chapter 255 of the manga.
WEL THERE IS SUPOSE TO BE A DUDE NAME IDASHI DAT WILL APPEAR AFTER THE WAR IS OVER
HE IS SUPOSE TO BE A SUVIVOR OF ITACHI'S DESTRUCTION BESIDES SASKUE...BUT WE WILL C IF THIS IS A SPOILER....I THINK IT IS PERSONALLY
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Idashi Uchiha made no (Public) appearences in Naruto Manga/Anime or Naruto Shippuden Manga/Anime. Idashi appeared in the story after Manga Chapter 250 of the Naruto Childhood series (Which Never aired to the public) . at some point of that duration Naruto fought Idashi to see who would be stronger and it turned out they were equal in terms of Strength.
If I am correct, Sasuke is his great great (etc.) nephew or grandson. But you should check another website first, because I'm probably wrong. :3 Hope this helped! :)
Itachi is the older brother of Sasuke Uchiha and is responsible for killing all the members of their clan, sparing only Sasuke. Itachi is treated as an antagonist for much of the series, however around the time of his death his villainous role is greatly downplayed. It is revealed that he was ordered by the former leaders of Konohagakure to kill the clan in order to prevent the Uchiha coup d'état which would have resulted in war. Despite his reservations, Itachi fulfilled his mission and defected from Konohagakure to become part of the criminal organization Akatsuki to continue protecting Konohagakure from behind the scenes. Itachi has not been featured in the films and original video animations from Naruto, but he is a playable character in most video games of the series. His character has been very popular within readers from the manga, having ranked high in various popularity polls from the series. Also numerous anime and manga publications have commented on Itachi's character. His fights are often noted to be "one of the best" in the series. His appearance as an antagonist has been praised by several writers although some considered his initial not to be very surprising. The gradual revelations of his past and its impact on the story has also been praised.Several types of merchandising have also been developed based on Itachi's appearance including figurines and plush.