Itachi didn't get MS at 13 you dumbass.
Eventually, at age 13, he was promoted to the rank of Anbu captain.[16] When the Uchiha clan began planning to overthrow Konoha, Itachi was tasked with exploiting his position to spy on the village. Knowing that a coup d'état would only trigger the beginning of another ninja-world war, Itachi became a double agent, feigning loyalty to the Uchiha while secretly passing on information about them to the Third Hokage and Konoha elders.[17] Itachi's best friend and brother-figure, Shisui Uchiha, opposed the coup d'état as well, but after having his right eye stolen by Danzō for its powerful Mangekyō ability, Shisui realised that it was beyond his power to stop the Uchiha clan's impending doom. Meeting Itachi in secret on a cliff overlooking the Naka River, he entrusted his remaining eye to him, requesting that Itachi protect the clan's good name before proceeding to "erase his existence".[18] The grief of losing his closest friend ultimately awakened Itachi's Mangekyō Sharingan, which he soon after used to read more of the secret stone monument.