I completely forgot about the merger and lowk don't even know what its for anymore buttttt, my favorite theory rn is that Yuji was the one who said domain expansion
Hmmmmm..........the merger is when kenjaku changed tengen using his curse manuplation also idts Yuji said domain expansion because we can see sukuna's hand sign which is for the domain but i believe more on the theory that it's just sukuna's hallucination
true we did see sukunas hand sign, but the panel where Domain expansion is said is a solid black panel, there would be no reason for that especially if you're going to have a huge reveal right after
Sukuna is soon going to start the merger because he is weak rn just like he did with Gojo and summoned mahoraga, To defeat the merger Gojo(one eye sacrificed to adjust power scaling)came because we know its nearly impossible at this point to defeat the merger and Sukuna at the same time, soooooo.......for the sake of the plot Gege revived Gojo just to fight the merger and Yuji fighting sukuna , this way the build up of Yuji's character won't get ruined; THE GHOST OF THE STRONGEST; JJK MANGA IS THE MOST TRENDING MANGA IN THE WORLD RN; AKARI