Jujutsu Kaisen Chapter 145: The Back

The chapter begins with the reaction of the cast to Tengen's form. As a community we were confused as to why Yuki didn't have a greeting and it's confirmed that they have actually met before which is a very nice revelation.

In the Star Plasma Vessel arc we saw Yuki assume that Tengen's state would be stable after Riko's death, but we get confirmation that Tengen was not able to assimilate with a Star Plasma Vessel due to some unforeseen intrusion with Toji.

If Toji did not intrude, the merging would have happened but since Toji is an anomaly, the link of fate between the SPV and Tengen broke and there wasn't a merger. Tengen has been slowly evolving for the last 11 years. https://twitter.com/SatorIzzy/status/1381279297244176391

Due to Tengen's barrier mastery he is able to maintain a form even after evolving. Even though he has a form his ego is around everything and he is one with heaven and earth. Omnipresent

The issue here is that since Tengen is "evolved" an assimilation with individuals who are not the Star Plasma Vessel is now possible. Merging with Tengen will cause people who merge with him to reach another level of existence.

Tengen's form is closer to that of a curse so he is now subject to the curse manipulation technique and can be taken in by Kenjaku which is why Tengen needs people to guard him incase Kenjaku comes.

What Kenjaku wants to do with the culling game is to increase the rate of successful merging with Tengen. Deepening the knowledge of the player's cursed energy allows a merge with humanity to be more successful.

In a short version Kenjaku doesn't have the Cursed Energy to turn all humans in Japan/the world to sorcerers, so he needs the Culling game to generate the Cursed Energy so that he can merge the individuals in the game with Tengen pushing humanity to the next level.

If an evil person merges with Tengen and reaches an evolved state, evil will spread. Just as Tengen's ego spreads throughout, an evolved individual's ego will spread aswell causing the world as they know it to be consumed in evil.

The "other side" is a reference to Nirvana. Kenjaku's plan is to use the culling game and Tengen to force humanity to evolve and reach an evolved state. https://twitter.com/SatorIzzy/status/1381281034495479809

The Culling game is a ritual to spear head humanity to the next level, to succeed in this Kenjaku disconnected himself from the game allowing him to move freely so he can conduct his plans. Even if you kill him the game will not end.

The game is very crucial.

The Sorcerers plan to create a rule that allows Tsumiki, and anyone who doesn't want to participate, the ability to leave the game since it doesn't go against the longevity of the game.

The next goal is to figure out how to free Gojo. In short you need the Entrance and Back Door of the Prison Realm in order to open it and the person with the power to open it freely is the one with the front door which is Kenjaku.

However, you can forcibly open the back door with the Inverted Spear of heaven or the black rope, but they were sealed/destroyed by Gojo. The only other option now is to talk with Hana Kurusu who has the ability to eliminate any cursed technique.