The Byakugan (白眼; Literally meaning "White Eye") is the dōjutsu kekkei genkai of the Konohagakure's Hyūga clan. The eye first manifested itself in Kaguya Ōtsutsuki, and was later passed down to her son, Hamura Ōtsutsuki; both of these remarkable beings are the progenitors of the prestigious Hyūga clan. Due to the Byakugan's immense visual capacities, possessing the greatest sight between itself and the Sharingan, the Byakugan is also known as the Eye That See Destiny (見命瞳, Kenmyōgan).
A Byakugan can evolve into a Tenseigan under unique circumstances; this was first showcased through Hinome Hyūga, the transmigrant of Hamura Ōtsutsuki. The Byakugan, Sharingan, and Rinnegan are the foremost dōjutsu in the Shinobi world; any other dōjutsu are genetic offshoots of one of these three, and as such, they have come to be known as the Three Great Dōjutsu (三大瞳術, San Daidōjutsu; Literally meaning "Three Great Eye Techniques").
The Byakugan manifested itself in a time before shinobi and villages; before even the Warring States Period (戦国時代, Sengoku Jidai), through Kaguya Ōtsutsuki, otherwise known as the Rabbit Goddess (卯の女神, Usagi no Megami) or feared throughout the world simply as the Demon (鬼, Oni). The Byakugan later manifested itself in the woman's youngest son, Hamura Ōtsutsuki, whose descendants, the Hyūga clan, would inherit the eyes.
Despite shinobi lore focusing almost solely on the Uchiha and Senju clan, the Hyūga, descended from Hamura, would go on to gain fame and recognition throughout the Warring States Period for the great insight of the Byakugan, which was gave the user an extended field of vision, the ability to see through solid objects, and to see chakra in all its forms, visual perception that outstripped anything an Uchiha could ever hope to achieve. Eventually, the eye became so coveted by enemies for its abilities, that the Hyūga clan, even before joining Konohagakure, devised a system to protect their Byakugan; a two-house system, containing the the Main House (宗家, Sōke) and the Branch House (分家, Bunke), in addition to a powerful juinjutsu that seals the eye a branch house member in the event of their death. This seal, however, also doubles as a way to inflict severe pain onto Branch House members as a method of punishing them for insubordination.
When the Hyūga joined Konohagakure, the Byakugan became a powerful asset to a growing village.
Among all dōjutsu in existence, the Byakugan is stated to possess the greatest insight and clarity, surpassing even the Rinnegan with its visual acuity. This shows itself strongest in the Byakugan's abilities — alone among the Three Great Dōjutsu are all of its abilities related solely to its sight.
Boiling down the dōjutsu's ability to a succinct summary, it would be extra-sensory perception (超能力 chōnōryoku), but this statement alone cannot cover every facet of the Byakugan's incredible visual prowess. The primary ability of the Byakugan, and quite possibly its most well known, is granting them a near 360º field of vision, with the sole exception being a blind spit located at the back of the neck above the first thoracic vertebra. At the moment of initial activation, a Byakugan user gains an automatic 50 metre field of vision that, on conjunction with their 360º field of vision, allows the user to see for 50 metres in any direction, effectively granting a form of telescopic vision. With intensive training, however, this limit can be extended to cover vast distances. The Byakugan can even magnify targets, to examine every last detail.
As the eye that sees through everything, the Byakugan is capable of seeing through solid objects, ranging from solid walls, titanium doors, and even the human body. They can also see clearly in darkness, smokescreens, and other forms of concealment, making stealth impossible in front of a Byakugan. However, there are some barriers that can distort the vision of a Byakugan, though these usually possess particularly strong or foul chakra. Similarly to the Sharingan, the Byakugan's enhanced perception allows the user to track fast moving opponents, however, like any eye, being able to track their movements is still pointless without a body that can match the force.
By far the most coveted ability of the Byakugan is its ability to see chakra in all forms; naturally, this extends to the flow of the chakra within the chakra circulatory system, the channels in the body that transer chakra in a manner akin to blood vessels, as well as the colour associated with the chakra of another individual. Seeing the chakra circulatory system is tantamount to performing the Hyūga clan's unique taijutsu, the Gentle Fist. The Gentle Fist takes full advantage of the Byakugan's advanced perception to attack the chakra circulatory system, and for advanced users, the tenketsu, nodes along the chakra circulatory system where chakra can be released. For a Byakugan master, they are capable of seeing the Eight Gates, eight specific tenketsu along the chakra circulatory system that regulate the chakra a person can use. Through the use of a high level Gentle Fist technique, a Hyūga can specifically shut down these tenketsu, blocking access to the Eight Gates entirely for a limited time.
The Byakugan's ability to see chakra in all forms extends to even the most minute amounts. When chakra is formed into large surges, or even solid objects, such as a Susanoo, the Byakugan's analytical skills surpass even that of a Sharingan. By observing the flow of chakra in an object such as this, the Byakugan's wielder can employ the Gentle Fist to strike where the target is weakest; disrupting its flow and damaging, or destroying, the object entirely. For a Byakugan master wielding Gentle Fist, there is no difference between the bones of a Susanoo and a brittle twig lying on the ground. However, the Byakugan does more than simply see the formations of chakra constructs. It also details to the more experienced user how much force would be required to break it or how much would be necessary to overload the stability of the construct itself. The larger the surge of dismantling energy employed, the easier it is to shatter the weak points of a defensive jutsu like Susanoo, thanks to the Byakugan's sharp analytics of the construct formed
A Sage who wields the Byakugan gains a very unique ability; the power to perceive natural energy in its purest state. This is referred to as witnessing the World Flow (界流, Kairyū), and can be considered something akin to the chakra circulatory system, only on a global scale. When a Sage witnesses the world flow in this method, the natural energy of the world isn't something they can fully comprehend; as the World Flow is the power of the world itself, and when an unprepared Sage can be overwhelmed by this power. The only similar sensation would be gauging the power of the Shinju, a beast stated to have the power equivalent to the planet itself. Byakugan which gain the ability to perceive the World Flow are called the All-Seeing White Eye (全智 白眼 Zenchi Byakugan).
Even while dormant, the eyes of a Hyūga or Ōtsutsuki clan member bear a stark difference from a standard human eye; the iris itself is white (with some Hyūga and Ōtsutsuki having hints of lavender), as well as far larger than the iris of a normal human, and the pupil is barely discernible. Due to the size of the iris, the sclera of the Byakugan is not as apparent as a normal human eye. When the eye of a Branch house member is sealed, it will return to this dormant state, and remains "locked"; should a ninja gouge out the eye and implant it in their own body, it will be of no use as it can no longer activate.
Notably, this 'dormant' stage of the Byakugan is only seen in a pure-blood Hyūga or Ōtsutsuki clan member. When a half-breed is born, their eyes are typically the colour of the non-Byakugan parent, and in this case, they are still capable of unlocking the Byakugan.
When activated, the Byakugan's appearance alters slightly. While retaining the same primarily white colour scheme, the hidden pupil becomes more apparent, enhancing the users ability to take in light, as well as allowing the Byakugan to perform its impressive feats of vision. Additionally, an activated Byakugan requires more blood and chakra than other dōjutsu, and thus, veins bulge near the temple of the Byakugan's wielder, increasing both the flow of blood and chakra.
When a half-breed Hyūga or Ōtsutsuki unlocks the Byakugan and they do not possess the traditional 'dormant' stage, the transformation in their eyes is far more drastic, changing from their current colour to the more traditional Byakugan image.
White Zetsu's dōjutsu
The White Zetsu that worked with Black Zetsu possessed a unique eye technique that greatly resembled the Byakugan both dormant and when activated, being a pupilless eye that gains a notable pupil when the user activates it to perform its intended function. The only stark difference, appearance-wise, is the colour; White Zetsu's eye is a dull yellow. Through this eye, White Zetsu witnesses an event and records it for a later playback, as he did for Obito Uchiha after Sasuke Uchiha's battle with his older brother, Itachi.
Given Zetsu's connection to Kaguya, this eye may be related to the Byakugan in some way.
Byakugan & Sharingan
Notably, if an Uchiha and a Hyūga were to have a child, a most unique event would take place. Within each eye, the hybrid child would unlock a Byakugan and Sharingan; one per eye.
The Sekireigan is not a variation of its own, but rather, an off-shoot of the Byakugan, found in members of Kirigakure's Gaki Clan. The eye displays similar penetrative powers, but it also displays unique abilities that resemble the Sharingan, pulling the user into an irresisible genjutsu that is not easily seen through — it can even fool the Byakugan itself. Uniquely, it also allows fo rthe manipulation of the user's life force. This Kekkei Genkai made itself known in Kirigakure.
Transplanting the Byakugan
As is the case with the Sharingan and Rinnegan, as well as any dōjutsu, the Byakugan can be transplanted to another individual. Theft of the Byakugan was common practice in the Warring States Period, and even in the modern era, the Byakugan's abilities are so coveted that any Hyūga who finds themselves slain in battle will have their eyes stolen by the victory. This was the case with Ao, an Anbu Hunter-nin of Kirikgakure, who slew a Hyūga in combat and transplanted the eye into his own right socket. Ninja from other villages who manage to obtain a Byakugan will go to amazing lengths to secure it; the most notable being Ao, who wears talismans on each ear that prevent his Byakugan from being removed, even by himself.
Due to the coveted nature of the Byakugan, the Hyūga have also taken great lengths to secure their clan's kekkei genkai. The development of the Hyūga Main Family's Juinjutsu, also referred to as the Caged Bird Seal (籠の鳥 封印 Kagonotori Fūin), was created to protect the kekkei genkai of the clan by sealing the Byakugan of members of the Branch family when they die, preventing the Byakugan from being stolen from a corpse. How the Hyūga protect the eyes of the Main family, however, is unknown, as Ao's eye is presumed to be from a Main family member.
Unlike the Sharingan or Rinnegan, a transplanted Byakugan can be activated and deactivated at will, and doesn't seem to drain as much chakra as either of the remaining two dōjutsu.
Obtaining the Tenseigan
As is the case with the Sharingan, the Byakugan has the capacity to return to its roots and evolve further into a dōjutsu that is not often seen, and equally as rare and powerful as the Rinnegan in its own right; the Tenseigan (転生眼; "Reincarnation Eye"). The Tenseigan is a dōjutsu that originally manifested in the Ōtsutsuki of old, beginning with Hamura Ōtsutsuki when it evolved from his Byakugan. The eye is unique to the Ōtsutsuki and Hyūga clans, in the way that the Rinnegan is unique to the Ōtsutsuki and Uchiha clans. Originally manifesting itself in Hamura, Hinome Hyūga is the first known person to manifest the Tenseigan in the modern world, due to being the transmigrant of the legendary figure.
Similarly to how the Rinnegan was a natural progression of the Sharingan when it reacted to Hagoromo Ōtsutsuki's immense sage chakra's, the Tenseigan originally manifested naturally in Hamura's eyes for the first time when he became a fully realized sage. This occured after the sealing of his mother, his power fully coming into its own when it resonated with his older brother. Hinome's own Byakugan evolved into a Tenseigan when she became a fully realized transmigrant of Hamura, reacting to his Sage chakra. This allowed her to achieve the status of Sage.
A Tenseigan retains all abilities it had as a Byakugan, but additionally, grants the user two unique abilities; Truth-Seeking Balls, and the Tenseigan Chakra Mode. A Tenseigan is also stated to have superior visual acuity when compared to a Rinnegan, despite its lack of fancy abilities.
The Tenseigan is highly vulnerable to stress; if a user who is new to the effects of the dōjutsu overexerts their chakra, or receives sufficient enough damage, the Tenseigan will 'fade'. By fading, sealing itself off from further use, it reverts to an ordinary Byakugan that will never manifest a Tenseigan again, and the effects from the Tenseigan while activated will dissolve. This does not hold true for a seasoned Tenseigan user, however it remains pertinent that a Tenseigan user who aspires to truly use the technique to its fullest train for an extended period of time before using the dōjutsu as a weapon.
- The Byakugan is believed to be the predecessor of the Sharingan. How much of this is true remains unknown, however, Kaguya Ōtsutsuki wielded the Byakugan naturally before unlocking the Sharingan and Rinnegan, and all three were wielded by her descendants, showing there is some truth to this claim.
- The World Flow concept was created by User:Silver-Haired Seireitou and is used with his permission.
- It has actually been stated by Masashi Kishimoto that if an Uchiha and a Hyūga were to have a child, the child would have a Byakugan and Sharingan, one in each eye.
- It is possible for those of diminished Hyūga blood to unlock the Byakugan should they be descended from the clan. Half-Hyūga can unlock the dōjutsu in both eyes; The Kohinata clan, a family descended from the Hyūga clan, are of such diluted blood that it is rarely unlocked, and only in a single eye.