As Ashitaka is dozing under the tree, he momentarily feels something touch the side of his head. Not a moment later is he screaming, falling flat on the ground with his arms flailing.
Ahhhhhhhhhhhhh!
He immediately got up and dusted himself off as he saw the Fuukage and heard her demands.
Genjutsu? Genjutsu is sort of like ninjutsu. You use your chakra to do things a regular person cannot do. But unlike ninjutsu, which usually results in external damage, genjutsu manipulates the flow of chakra in your opponent's brain to induce illusions or control one or more of your five senses. There are many different kinds of weird and sadistic illusions to be seen. The sharingan is a dojutsu that is famous for both casting and defending against genjutsu. Genjutsu usually falls under yin release too. Dojutsu, hand signs, sound, etc. can be the trigger for many genjutsu. There are four ways of breaking genjutsu. Physical pain, full body surges, genjutsu kai, and someone else surging their chakra into your body. The thing with full body surges, the surge has to be one rank above the genjutsu for it to break. An example would be Chidori Nagashi being able to break the Snake Crushing Genjutsu. Unfortunately, Chidori Nagashi cannot stop the Bringer of Darkness Genjutsu, but the Bringer of Darkness only takes away your eyesight. As such, you can hear, smell, touch, and if you wanted to, taste your opponent. Notable genjutsu users are namely Itachi Uchiha, Obito Uchiha, Shisui Uchiha, Kurenai Yuhi, and The Second Mizukage.