Genjutsu (幻術 lit. Illusion Techniques) is one of the main Jutsu categories, the others being Ninjutsu, Taijutsu, and Senjutsu.
Genjutsu can be broadly classified based on casting method:
- Ocular Genjutsu
- Sound-based Genjutsu
Note that most Genjutsu affect all five traditional senses. Ocular Genjutsu, for example, does not affect only the victims vision. Ocular Genjutsu, while cast with an eye, does not necessarily require eye contact with the victim.
What it is
While we all can identify Genjutsu by looking at what it does, it does have a formal classification. Traditionally, Chakra is considered to be made up of Spiritual Energy (Yin/Imagination) and Physical Stamina (Yang/Vitality). All Genjutsu consumes only spiritual energy, just like all Taijutsu consumes only physical stamina.
Ocular Genjutsu is pretty much exclusive to the Sharingan (写輪眼 lit. Copy Wheel Eye), which typically has two powers.
- "Eye of Hypnotism" allows one to cast a generic Genjutsu through eye contact.
- "Eye of Insight" allows one to copy another's use of technique, but it's true function is to anticipate and counter attacks like Genjutsu.
This is why the Sharingan is considered as the eye of Genjutsu in the Three Great Dojutsu, the others being Byakugan (Taijutsu) and the Rinnegan (Ninjutsu). There is one more eye which is Tenseigan (Senjutsu) but that is unknown to the Shinobi on Earth until Toneri's attack in the Last.
What it is used for
Genjutsu can be further classified into how it is used. In order of difficulty:
- Reality Manipulation
However, this is not a definitive way of classifying them as the same technique can be used with multiple different application depending on the users' needs. For example, the Sharingan Genjutsu was used for Immobilisation, Control and Projection before. Izanagi was used for projection to manipulate reality but it also immobilise the victim at the same time.
The most basic use of Genjutsu is immobilisation, where the victim is temporarily paralysed or even loses consciousness. This was proved to be simple and can be casually done even with only the basic Sharingan, especially on fodder Shinobi. Sasuke was able to use this to knock Sakura out with a glance, even with the Bijuu still trapped in his Genjutsu.
Other than with the Sharingan, it was also used by Jiraiya's sound-based Genjutsu, Gama Rinsho, on the Six Paths of Pain. Unlike the Sharingan Genjutsu, this is purely for paralysis with no mental projection involved. The same applies for Tayuya's Phantom Sound Chains.
The most powerful application of this is by Sasuke, which was able to immobilise all nine Tailed Beasts at once, with a single glance. While a regular Sharingan is able to control the Nine-Tails, this level of Genjutsu apparently can only be done by the likes of Rinne Sharingan, possibly also with the help of Six Paths Chakra, as even Hagoromo himself was mildly surprised by it.
Genjutsu is most commonly used for control especially for middle-ability Ninjas. The lowest level of application would be considered as Hypnotic Genjutsu, which suggests to the opponent their next move.
Higher levels of application would be for interrogation, like when Itachi was able to force information out of his victims. Such a Jutsu requires greater chakra control. Both Sasuke and Obito was able to use just the basic Sharingan to accomplish this. Unlike hypnotic Genjutsu, the victims have no recollection of the process.
This can be done even when the victim is already unconscious. For example when Kabuto's mind was stuck in the Izanami loop, Itachi was still able to use Sharingan Genjutsu cast from a Mangekyo Sharingan to control his body into releasing the Edo Tensei Jutsu.
Itachi also used his Sharingan to control his crow into flying out of Naruto and even casting Koto Amatsukami onto himself. This means that one can have potentially a long chain of Genjutsu commands from one to another.
The most powerful of this is definitely Shisui Uchiha's Koto Amatsukami, the most powerful Mangekyo Sharingan Genjutsu. Now many people don't know this but like any other Mangekyo Sharingan, Shisui has two different versions Koto Amatsukami in each eye.
The left Koto Amatsukami gives direct instruction to the target, becoming his "ideal" to work towards to. When Itachi used it on himself, it did not seem to have manipulated any memory. On top of that, Edo Tensei can control Itachi regardless of what memory defines him, hence such an action wouldn't have been able to help him overcome the Edo Tensei.
Once the Jutsu is cast, it's effect is permanent on the target, regardless of what happens to the caster. After the Mangekyo Sharingan went back to being a regular Sharingan, and even after the Mangekyo Sharingan was destroyed by Amaterasu, Itachi remains free from Kabuto's control.
There are two types of Genjutsu for projection: subtle and obvious.
The right Koto Amatsukami, the one stolen by Danzo, is an example of Subtle Projection. Whatever it projected was seen by the victim as past experiences, hence acting to the caster's wish completely out of their own free will. (which doesn't classify as "control")
Contrary to popular belief, Koto Amatsukami does not work directly on the brain, and like most other Genjutsu, works on controlling the victim's chakra. However, Koto Amatsukami does not seem to require eye contact as Danzo was able to cast it on Fourth Mizukage without removing the bandages covering his right eye.
Obvious Projection is much easier to perform, albeit still harder than mere immobilization. Madara could cast it on Obito with just the basic Sharingan, but only with the Gedo Mazo was he able to control the dream to any detail. Itachi was able to relay memories to Sasuke, but without the Mazo, he does not have the same control as Madara.
Unlike the subtle projection, the victims know that they are in a Genjutsu.
Itachi's Mangekyo Sharingan ability Tsukuyomi uses this to subject his victims to days' worth of torture in a matter of seconds. According to Kakashi, whether one has the way to escape this Genjutsu doesn't matter. Once being caught in this Genjutsu, Itachi is able to freely manipulate even the passing of time, so that a few seconds can feel like days.
The greatest form of the application comes in the form of Infinite Tsukuyomi, where the Jutsu is reflected off the Moon instead of being cast from the eye. It isn't just a Genjutsu to immobilize them temporarily, it is putting the victims into dreams and forcing them to accept their reality, despite knowing that they are in a Genjutsu.
However, this Jutsu consumes an immense amount of chakra. After Madara cast Infinite Tsukuyomi, his 9-Tomoe Rinne Sharingan was reduced to having just 6 Tomoe.
In the 6th Naruto movie, there is also a watered-down version called Limited Tsukuyomi, cast by a Rinne Sharingan with only 7-Tomoe.
While reality manipulation sounds totally out of the world, Izanagi really is just the reverse of a typical Genjutsu. While other Genjutsu turn dream into reality, Izanagi turns reality into dream. As a result, the Jutsu was able to change destiny.
However, it was only able to ignore certain events, which users usually use to cheat their own deaths.
While it was originally said to only can be used by those with both Sharingan and Hashirama's cells (Danzo and Obito), it was later revealed that one with the Mangekyo Sharingan was able to use it as well (Madara and Itachi).
Unlike Izanagi which is purely reality manipulation, Izanami also involves immobilizing the victims while the events play inside the victim's mind. According to Itachi, Izanami does not require eye contact, as it works on the caster and opponents' senses to recreate the same sensation, in order to loop the events in-between.
And the most powerful of this application is none other than Creation of All Things Technique used by Hagoromo himself to create the souls Nine Tailed Beasts from his own imagination. The part where he gave them physical form, however, is not part of Izanagi's power, but the Yang side of it.
How it works
According to Jiraiya, Genjutsu works on opponent's five senses by controlling the chakra flowing through the cranial nerves. This applies to most Genjutsu, such as the generic Sharingan Genjutsu and Tsukuyomi.
However, not all Genjutsu does that. Izanagi and Izanami does works outside of Chakra.
However, this does not work on just usable chakra but energy in the broader sense, as we've seen animals being trapped in the Infinite Tsukuyomi, or the Nine-Tails being subdued by Madara's generic Sharingan Genjutsu (despite the Nine-Tails having no chakra pathway system).
How to counter it
Since most Genjutsu works by manipulating the chakra flowing through the cranal nerves, the most straightforward way to counter the Genjutsu is to disrupt your own chakra flow, also called Genjutsu Kai (幻術解 lit. Illusion Technique Dissipation).
While it is easy for a third party to do it, releasing yourself from a Genjutsu presumably requires great spiritual strength to create a chakra disruption large enough to offset the original.
While Tailed Beasts themselves are susceptible to Genjutsu, they can easily release their Jinchuriki from a Genjutsu, provided that the two are in good terms. Otherwise, not only can the Sharingan user control the Jinchuriki (Yugara), one can also control the beast itself (Kushina).
One can also break a Genjutsu by being subjected to a more powerful Genjutsu. Through their Mangekyo Sharingan, Sasuke and Itachi used Sharingan Genjutsu and Tsukuyomi respectively to break each other out of Kabuto's Phantom Sound Chains.
In the anime, Genjutsu Tree Village uses Chilli Pepper Bomb to break out of Genjutsu by triggering the sense of smell.