That Day…!! (その日…!!, Sono hi…!!) is chapter 224 of the Naruto manga.
Sasuke asked his mother about Fugaku, wondering what their father really thought of him and Itachi. She assured him that Fugaku only ever had words of praise for Sasuke and that his interest in Itachi was only for the Uchiha clan's benefit. Soon afterwards, Sasuke returned home one night to find all the members of his clan dead; murdered by Itachi. Itachi used his Mangekyō Sharingan to torture Sasuke and destroy the facade of a loving older brother he had assumed for so long. Explaining to have killed the Uchiha to measure his abilities, Itachi added that Sasuke now represented his greatest challenge. If Sasuke were to grow up hating him and acquire the Mangekyō Sharingan, they would be a match. However, to gain it, Sasuke would need to kill his closest friend.