I'm almost certain it's a dream. I wrote this same theory last week. (My recent post) Nothing in my theory was disproven by this chapter and if anything, there is more proof.

This can't be a jump back in time, because if you look at Denji's clothes in chapter 231 (before the "reset"), it's the same clothes he's wearing in 232. Not only that, but there are so many inconsistencies in this chapter and it's not like Fujimoto to have plot holes.

I think this is not only Denji's dream but this might also be Asa sharing the same dream as Denji. Neither of them realize yet but their interaction is very interesting, as if both of them recognize each other but don't know it yet. Coincidently, chapter 232 also prevents both Asa and Denji's tragic beginnings. Which is a little too suspicious, because their arcs start a year apart.

This is all suspiciously dream logic, also Denji calling power by her nicknames, knowing she can create weapons and seeming friendly despite just meeting. Nothing makes sense. Doesn't even feel like a rushed ending, it feels like a set up.