Itachi had already extracted Sasuke's left eye. Itachi then told him that Sasuke wouldn't stand a chance against him since he didn't have the Mangekyou Sharingan. Itachi was about to pluck the other eye out when Sasuke activated his Curse Seal. Itachi kept the eye which he had removed into a glass jar and his shadow clone appeared right behind Sasuke. As Itachi moves in to take his remaining eye, Sasuke manages to overcome the Tsukuyomi he was placed under. Zetsu assumed that Sasuke had lost the battle after receiving a direct hit from Itachi's Tsukuyomi. However, both Itachi and Zetsu were surprised when Sasuke stood up, seemingly unharmed. It was then explained that even if a person only has a pair of normal Sharingan eyes, he's still able to defeat one with the Mangekyou Sharingan with higher levels of skill and power.
After Sasuke escaped Tsukuyomi, all genjutsu between the brothers became pointless. Itachi was forced to shift from his most powerful genjutsu to his most powerful ninjutsu. They both then engaged in fire style jutsu, with Sasuke gaining the upperhand. As opposed to Tsukuyomi, which originated in Itachi's left eye, the Amaterasu, a black flame said to burn forever, came from his right eye. In the battle with Sasuke, Itachi's eyes were strained to the point that he drew tears of blood while executing Amaterasu. In the struggle, Itachi activates Amaterasu, which seems to severely injure Sasuke.
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