|Literal English||Moon Reader|
|Appears in||Anime, Manga, Game, Movie|
|Classification||Kekkei Genkai, Genjutsu, Dōjutsu|
Tsukuyomi is a Mangekyō Sharingan dōjutsu and is one of the most powerful genjutsu in existence. It is said to represent the "Spiritual World and Darkness" (精神界と闇, Seishinkai to Yami) and is the antipode to Amaterasu.
Tsukuyomi requires eye contact to be performed. When executed, the technique traps the target in an illusion that is completely controlled by the user. Itachi's prowess with the technique has allowed him to alter the perception of time with ease within the genjutsu to make it seem to last for days when in fact it only lasts a few seconds. This allows him to torture the target for what seems like days on end, causing mental trauma that will render them unable to fight for an extensive period of time. After Itachi used it on Kakashi in Part I, Kisame was surprised that Kakashi was still alive. Only Tsunade has been shown capable of curing this psychological damage.
In the anime during Part I, Itachi's use of Tsukuyomi typically featured a red moon casting a red light throughout the illusion with a cloudy atmosphere, giving the background a blood-red appearance while the victim within the illusion is in depicted in an inverted grey scale.
Such a powerful technique is not without its disadvantages however. Due to the complexity of the illusion and the quickness with which it is executed, an enormous amount of chakra is necessary and an added amount of stress is placed on the left eye, leaving Itachi's vision more blurred. Before using it on Kakashi in Part I, Itachi stated that Tsukuyomi can only be broken by a Sharingan user that shares the same blood as him; as demonstrated when Sasuke overcame Itachi's Tsukuyomi in their battle. Sasuke can also perform Tsukuyomi with his right eye, though his illusion is considered inferior to Itachi's Tsukuyomi since it does not alter the opponent's perception of time indicating he has yet to master it.