Getting caught in a Genjutsu is complete misery, but it can be avoided with one simple rule. Does Itachi need eye contact for Genjutsu?
Yes, Itachi does need eye contact for certain Genjutsu. He can cast medium-level Genjutsu without eye contact, but Itachi needs it for his advanced techniques, like the Tsukuyomi.
Making eye contact is how Sharingan users trap their victims in their Genjutsus. Other Genjutsu ninja have their own methods for trapping people, but Sharingan users have eye contact rules for some of their specific techniques..
Might Guy confirms that Itachi requires some level of eye contact during a city fight against the rogue ninja.
Might Guy explains Itachi’s need for Genjutsu eye contact
In chapter #143, Might Guy jumps into the fight against Itachi and Kisame. The ninja on the scene, Asuma and Kurenai, alert Guy to not look Itachi directly in the eyes. He says he already knows that after years of training bouts against Kakashi’s Sharingan.
Guy says that when going up against someone with the Sharingan, you only need to avoid meeting your opponent’s eyes. “Just keep your sight on their feet at all times, and you can still read their movements and react.”
Asuma mentions that Guy may be the only one who can use that technique effectively. It’s easier said than done, as there are not many Sharingan users around to train with. Discerning an opponent’s movements just from their feet is a challenge for Asuma and Kurenai.
Guy instructs Kurenai to carry Kakashi to the medics and for Asuma to back him up. They only need to stall for time until the recently alerted Anbu Black Ops arrive on to the scene.
Before the Anbu can arrive, Itachi alerts Kisame that they’re going to leave. Itachi and Kisame came to the Leaf Village for a purpose, not to start street fights that only lead to negative attention.
So that’s the answer. Itachi does need eye contact for certain Genjutsu, as that’s how he traps people inside it. It’s a requirement of advanced Sharingan techniques to make eye contact with your victim before trapping them inside of a Genjutsu.