Yatagarasu (Ten Tails)

Yatagarasu is said to be one of the of the Uchiha Clan. It is only usable by a select few among the clan and—among them—only those who have awakened the Mangekyō Sharingan.

Usage
Like most Sharingan genjutsu, Yatagarasu requires eye contact in order to cast its illusionary effects. The purpose of the genjutsu is to blank a target's memory of the user. Saburō Uchiha first used this technique to erase the mind of Might Sai after being caught infiltrating the in Konohagakure. The danger of the technique is that it "perfectly" erases the memory the user wishes to delete, leaving no room for the target to subconsciously hold onto the memory, and thus eliminating the chances of the memory resurfacing.

Such power is not without consequences, however, as the Yatagarasu requires ample chakra and can be broken by other users of the Mangekyō Sharingan before memory loss occurs.

Improvement
By projecting the dōjutsu onto a mirror-like medium, the genjutsu will then radiate out, turning it from a short-range technique into one of long-range. This allows the user to affect a large number of targets at once. When used in this manner, it becomes much more difficult for a Mangekyō Sharingan user to effectively counter the technique with their visual prowess, though it should be noted that particularly skilled users of the heightened Sharingan can still dispel the illusion before it is able to affect their memory.

Influence
, the Crow-God himself, is symbolic specifically of guidance. This great crow was, according to legend, sent from heaven as a guide for on his initial journey from the region which would become Kumano to what would become Yamato. It is generally accepted that Yatagarasu is an incarnation of Taketsunimi no mikoto, but none of the early surviving documentary records are quite so specific.