For everyone trying to understand, basically the Big Bad Guy (the one controlling Geto's body) is trying to turn non-sorcerer people of Japan into curse users (cause he believes that sorcerers are the 'evolution') but to do that he needs a HUGE amount of power, so he has been scheming a big plan all this time for which he needed Geto's ability, to get the Six Eyes user out of the way (Satoru) and Tengen's evolution (by not being able to merge with the star plasma vessel). Tengen evolved into something that is more like a curse than a human (he used to be a human curse user) so now the Big Bad Guy can control him thanks to Geto's ability (of controlling curses) and use Tengen's powers to turn all Japan's population into curse users. And this will be really really BAD. Sukuna and Yuuji are of some use on all this plan but is not explained yet. Due to the attitude of the characters we can also suppose that Satoru got rid of the weapons that could freed him of the Prison Realm on purpose, because he knows more than he has said and has his own plans.
For everyone trying to understand, basically the Big Bad Guy (the one controlling Geto's body) is trying to turn non-sorcerer people of Japan into curse users (cause he believes that sorcerers are the 'evolution') but to do that he needs a HUGE amount of power, so he has been scheming a big plan all this time for which he needed Geto's ability, to get the Six Eyes user out of the way (Satoru) and Tengen's evolution (by not being able to merge with the star plasma vessel).
Tengen evolved into something that is more like a curse than a human (he used to be a human curse user) so now the Big Bad Guy can control him thanks to Geto's ability (of controlling curses) and use Tengen's powers to turn all Japan's population into curse users. And this will be really really BAD.
Sukuna and Yuuji are of some use on all this plan but is not explained yet.
Due to the attitude of the characters we can also suppose that Satoru got rid of the weapons that could freed him of the Prison Realm on purpose, because he knows more than he has said and has his own plans.