Tengen/Synopsis

History
During the Nara Period, Master Tengen spread Japanese Buddhism and preached what would become the foundation for jujutsu sorcerers.

Gojo's Past Arc
In the modern age Master Tengen does not interact with the outside world. They use a barrier technique to protect both jujutsu schools and to strengthen all of the auxiliary managers barrier techniques. Their immortality cursed technique must be reset once their body reaches a certain age. The technique will attempt to change bodies, forcibly evolving Tengen to a higher state, losing their will and potentially making them an enemy to humanity.

In order to prevent this, every five hundred years, Master Tengen must merge with a compatible star plasma vessel to rewrite their body's information. Once the body is refreshed, the cursed technique will be reset as well. In 2006, the Star Plasma Vessel was Riko Amanai.

Two groups targeted the girl; the curse user group Q who aimed to overturn the jujutsu world by having Tengen lose all reason, and the Time Vessel Association, the star religious group that worshipped Tengen as their deity. In order to ensure Riko's safety, Master Tengen had Masamichi Yaga assign his students Satoru Gojo and Suguru Geto with escorting the girl to Jujutsu High before the merger on the full moon.

Riko is ultimately assassinated by Toji Fushiguro who was contracted by the Time Vessel Association to kill the girl and prevent the impure merger. Even so, Master Tengen was somehow able to stabilize according to Yuki Tsukumo.

Culling Game Arc
When Yuki along with Yuji, Megumi, Maki, Yuta and Choso enter the shrine and find nothing. Yuta tells them to leave because Tsumiki doesn't have time, however, just then Master Tengen appears in front of them and greets them all. Yuki confronts Tengen, asking aren't they going to say hello to her while Tengen replies that it wasn't the first time that they've met. Yuki asks why they closed off the Tombs of the Star Corridor where they reveal that they were afraid they were aligned with Kenjaku, someone who Yuki doesn't recognizes and asks who they are. Tengen reveals that Kenjaku was the sorcerer who was once Noritoshi Kamo but now has inhabited Suguru Geto's body. Yuji suddenly interrupts the conversation and asks why Tengen looks the way they do who says that although they're immortal, they aren't immune to aging. They also add that in 500 years, he will look the same way as they are which surprises Yuji. Tengen tells them that 11 years ago after they failed to merge with the Star Plasma Vessel, their age accelerated and self awareness as an individual diminished and the very world became themselves.

Megumi and Yuta interrupt the conversation asking about Kenjaku's objectives and also how to open the Prison Realm. Tengen tells them they wished they could've simply said yes but on the condition of having Yuki Tsukumo, Yuta Okkotsu and or Choso to remain as his two guards. Yuta wonders why they need two guards despite them being immortal while Maki asks if it's because of the seal. Yuki objects to this saying that they haven't told them why and how long they need to do it. Tengen then explains Kenjaku's objective is to force the evolution of human kind throughout Japan. Megumi tells them that they are aware of of this and asks what exactly does Kenjaku intend on doing, and why didn't he turn everyone in japan into jujutsu sorcerers in Shibuya. Tengen explains that Kenjaku lacks the cursed energy to do so, they add on that the method he has chosen is to merge humankind with themselves. Choso wonders how this is possible because they're just one person where Tengen explains now that they've evolved over the past 11 years, it isn't impossible for them to merge with someone other than a Star Plasma Vessel.

Tengen explains that they possess barrier techniques which enable them to maintain their current form and self control even after evolving. They add that if humankind evolves and only one person rages out, the world will end. Yuki asks them why who says that the impurities of a hundred million people would flood the world, and what happened to Tokyo would happen to the entire world as well. The boundaries between individuals would cease to exist so evil would instantly spread to one another. Yuji asks Tengen why Kenjaku would do this who is unsure why because they cannot read human hearts.

When Maki asks why they refuse to merge, Tengen says that there is a problem. Now that they've evolved, they are more cursed spirit than human which makes them a target for cursed spirit manipulation, a revelation that shocks everyone. They add that considering Kenjaku's abilities as a sorcerer, he may be able to seize them the moment they encounter each other and that is the reason why their main body is rejecting everything at the Tombs of the Star Corridor. Yuta wonders if this is the reason why Tengen wants guards who confirms it. Tengen tells them that Kenjaku is the second most powerful barrier user behind themselves and they are unsure when he'll undo the seals on the tomb. Yuki asks why now of all times considering that he prevented Tengen's merging with a Star Plasma Vessel, forced their evolution and also wants to consume and control them through cursed spirit manipulation. She adds that he was apparently involved with Sukuna and has been a sorcerer for at least 1,000 years. Tengen tells her that themselves, the Star Plasma Vessel and the Six Eyes are all connected by faith.

Tengen reveal that Kenjaku lost twice to a sorcerer with the Six Eyes and the second time he took no chances and killed both the Star Plasma Vessel and the Six Eyes less than a month after they were born. Nevertheless, on the day of the merging, both the Six Eyes and the Star Plasma Vessel appeared. Upon which Kenjaku switched to sealing instead of eradicating the Six Eyes and thus began searching for the Prison Realm because two bearers of the Six Eyes cannot appear at the same time. However, the unexpected happened 11 years ago when Toji Zenin intervened. Tengen tells them that he was physically gifted through a Heavenly Restriction and was an anomaly who had zero cursed energy and destroyed their destiny. Then came a boy with curse manipulation, where all the pieces suddenly came together other than for the Prison Realm which fell into his grasp six years ago.

When Megumi asks why the culling game is happening, Tengen explains the culling game uses the participants and the boundaries binding barriers in a ritual that conveys the human beings of this country to the other side. And with that, Kenjaku will begin the merging with themselves, however, to perform the ritual, he has undertaken certain binding vows. One of the vows stipulates that he isn't the game master and this game doesn't work in their favor because even if Kenjaku is killed, the culling game will continue until all participants are either dead or the players refuse to participate and die. Yuji notices that Megumi is upset by this but is unsure why. Yuta concludes that they have no other choice but to participate and add a rule that allows Tsumiki and other unwilling participants to safely get out. Megumi adds that they also should free Gojo sensei because he would be able to settle everything on his own. Yuji looks over at Master Tengen and asks for them to tell them but they say to first decide who should remain as guards.

Much to the surprise of both Yuji and Megumi, Yuki and Choso step up for that position. Choso tells Yuji he will absolutely need either Okkotsu or Yuki's cooperation especially if Kenjaku comes for Tengen. Tengen thanks the group before pulling out a box that is the "back" of the Prison Realm. Tengen explains that before Kenjaku found the Prison Realm, it was outside of their barrier who believes it was overseas and reveals that by sealing the rear gate, they were hiding the existence of the "front" but it was useless. Yuji asks if it's like a back gate which Tengen confirms it is. Tengen tells them that Gojo is sealed inside of the rear gate as well and that the authority of opening the gate rests with Kenjaku as he is the bearer point of the "front". They add on that to break it open, they will need either the Inverted Spear of Heaven that nullifies cursed techniques and or the Black Rope that disrupts and cancels cursed techniques effects.

Yuji and Megumi are shocked because Gojo either sealed and or destroyed the Inverted Spear of Heaven 11 years ago but Yuta tells them that he along with Miguel searched for the Black Rope in Africa but to no avail. Yuki asks Tengen if there's a way who confirms there is. Tengen reveals that among the players participating in the culling game, there is a sorcerer from 1,000 years ago who calls herself an Angel and that her cursed technique can extinguish any cursed technique. Tengen then reveals the only other way to forcibly free Gojo from the Realm: through the cursed technique of an ancient sorcerer, Hana Kurusu, which can extinguish any cursed technique.