The Tenseigan (転生眼, Literally meaning: Reincarnation Eye) is a heightened stage of the Byakugan, similar in principle to the Rinnegan. It is only seen very rarely in the Ōtsutuki Clan, and even more rarely still, in members of the Hyūga clan. Rivaling the Rinnegan in power, the Tenseigan stands apart from the "Three Great Dōjutsu" (三大瞳術, San Daidōjutsu, Literally meaning: Three Great Eye Techniques). It is known among the Ōtsutsuki as the Eye that Sees Despair (見絶瞳, Kenzetsugan).
The Tenseigan is a dōjutsu that originally manifested in the Ōtsutsuki of old, seeming to begin 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.
Hamura is not the first of the Ōtsutsuki to manifest the Tenseigan, however, similarly to how the Rinnegan did not debut into the world with Hagoromo. In older Ōtsutsuki legends, the Tenseigan is a revered eye, spoken of which as much acclamation as the Rinnegan itself. The first known Ōtsutsuki to possess the Tenseigan was a powerful Clan leader, whose name would go on to be lost to history. His monicker, however, would survive on ancient, semi-destroyed stone tablets on the Ōtsutsuki homeworld. This Ōtsutsuki was the "White Yaksha" (城夜叉, Shiroyasha). Together with his comrade, the "Heavenly Yaksha" (天夜叉, Tenyasha), the original Ōtsutsuki to manifest the Rinnegan in its many forms, the two would originally try to unite their extraterrestrial clan.
The abilities of the Tenseigan are the most distinctive among any known dōjutsu. Much like a fully-evolved Rinnegan (i.e. one with tomoe), the Tenseigan dōjutsu retains the abilities it once-held as a Byakugan, however, they are vastly heightened. The user's visual acuity surpasses the Rinnegan and Byakugan by far — to compare the two to the Tenseigan is to compare the distance between worlds. The distance to which one can see with a Tenseigan varies by user, as it does with the Byakugan, however, the limit of the Byakugan is paltry in comparison to the Tenseigan itself; a Tenseigan user has been known to see vast distances, halfway across what one could consider a country border.
The most keen ability of the Byakugan, to bore into a target's body visually and see the Chakra Pathway System remains; a Tenseigan user can now bear witness to the existence of the chakra limiters, the Eight Gates, with the pinpoint accuracy of a master marksman. Capitalising on their ability to see the Pathway System and Eight Gates, a skilled Tenseigan wielder can completely destroy an opponent's ability to wield chakra, disabling them and rendering them unable to mould the critical energies ever again. The Tenseigan comes with the innate ability to perceive natural energy in its purest state — normally a trait only usable by a Byakugan user that has mastered Senjutsu. This is referred to as witnessing the World Flow (界流, Kairyū).
In spite of these already fearful abilities, the Tenseigan possesses tricks that the Byakugan never could. While being the Byakugan's only evolution, the Tenseigan is not in the same class as the Mangekyō Sharingan, and are in fact, the eyes of a Sage. As such, its strengths do not lie in the eyes themselves. Ōtsutsuki such as Hamura Ōtsutsuki, or Hyūga Clan members who are his transmigrants or direct descendants, can utilise the purity of this chakra in conjunction with their eyes and bring out a new source of strength: the Tenseigan Chakra Mode (転生眼チャクラモード Tenseigan Chakura Mōdo), a heightened transformation unique to Tenseigan wielders by virtue of possessing these blessed eyes.