Genjutsu are techniques that use the chakra in the victim's nervous system to create illusions; basically an advanced intellectual ninjutsu. Those with special abilities like the Uchiha clan's Sharingan or those with high intelligence have an easier time executing and countering genjutsu, since attention to detail is key. The most commonly seen genjutsu is the simple creation of phantasms – causing the targeted person(s) to hear, see, smell, taste and/or feel sensations that are not actually there in order to manipulate them. In other words, genjutsu affects the five senses, though other applications of genjutsu exist. Those under the influence of genjutsu either freeze in place or lose consciousness, depending on how capable they are in recognizing and defending against it.
There are several ways to counter genjutsu. Because it uses the victim's own chakra against them, the target can cancel the genjutsu by disrupting their own chakra flow. This is called Genjutsu Cancel. Alternatively, should they fail to cancel the genjutsu, intense pain (though not that caused by the genjutsu) can snap them out of it, as shown in the battle between Shikamaru Nara and Tayuya, when Shikamaru used his own shadow to break his finger in order to snap himself out of Tayuya's Demonic Flute Illusion genjutsu. Finally, someone else can disrupt their chakra flow for them through physical contact. The level of a genjutsu determines the difficulty in breaking it.
Name: KokuangyÅ� no Jutsu, literally "Bringer of Darkness Technique", English TV "Genjutsu: Infinite Darkness Jutsu"
Type: A-rank, Supplementary, Short to mid-range (0-10m)
Users: First Hokage (manga only), Second Hokage (anime only)
This jutsu makes the target think that they are surrounded by total darkness, allowing the user to attack unseen. In the anime, the Second Hokage was the one to initiate this technique. In the manga, it was the First Hokage.
Death Foreseeing Technique
Name: Shi no kumi no Jutsu, literally "Death Foreseeing Technique" or "Death Viewing Technique"
This jutsu is much like the Temporary Paralysis Technique, but paralyzes the foe by showing them a vision of their own gruesome death. In addition to the paralysis, the enemy is overwhelmed with fear, and can suffer severe mental stress.
Demonic Illusion: False Surroundings Technique
Name: Magen: Kokoni Arazu no Jutsu, literally "Demonic Illusion: False Surroundings Technique" English TV "Sly Mind Affect Jutsu"
Type: C-rank, Supplementary, All ranges
Users: Kotetsu Hagane, Oboro
This jutsu changes the appearance of a nearby object or area.
Demonic Illusion: Hell Viewing Technique
Name: Magen: Narakumi no Jutsu, literally "Demonic Illusion: Hell Viewing Technique"
Type: D-rank, Supplementary, Short range (0-5m)
Users: Kakashi Hatake
This jutsu causes the target to see a horrifying vision. First, an imaginary circle of leaves will spin around and envelop the target, falling away shortly after. After a short period, the illusion will begin. This is to make the illusion more convincing, since the user will likely have moved before the illusion sets in.
Demonic Illusion: Mirror Heaven and Earth Change
Name: Magen: KyÅ�ten Chiten, literally "Demonic Illusion: Mirror Heaven and Earth Change", English TV "Genjutsu Reflection"
Type: Kekkei genkai, No rank, Supplementary, Short range (0-5m)
Users: Itachi Uchiha
Using the Sharingan's jutsu-copying abilities, Itachi can reverse any genjutsu back on its original user.
Demonic Illusion: Tree Bind Death
Name: Magen: Jubaku Satsu, literally "Demonic Illusion: Tree Bind Death", English TV "Genjutsu: Sylvan Fetters", English games "Tree Capture Death"
Type: B-rank, Supplementary, Short range (0-5m)
Users: Kurenai Yuhi, Kurama clan members, Sakura Haruno (Naruto: Ultimate Ninja)
With this jutsu, the user can make themselves disappear, allowing them to approach their target unnoticed. Once completed, a tree and roots will grow at the target's feet and restrict their movements. Once the opponent believes that they are captured, the user can then appear above their opponent from the tree's trunk and kill the target. In the Kurama clan filler arc of the anime, this jutsu seems to be quite versatile, with a wide range of variations on the standard nature theme. In addition to the disappearing and tree-growing effects of the jutsu, the user can produce flowers, seedpods, vines and multiple trees.
Temple of Nirvana Technique
Name: Nehan ShÅ�ja no Jutsu, literally "Temple of Nirvana Technique" English "Nirvana Temple Jutsu" English Games "Feather Illusion Jutsu"
Type: A-rank, Supplementary, All ranges
Users: Kabuto Yakushi
This jutsu causes everyone within a specific area to fall into a deep sleep. From the target's point of view, it seems as if feathers are falling from the sky, which serves as a distraction to allow the jutsu to take effect. The downside, however, is that it takes a fair amount of time to take effect, and any experienced ninja has more than enough time to dispel it.