You know the entire event I was noticing stuff that felt incongruent. Everyone was acting like at least post 4.2, they referenced Swimsuit 2 and Swimsuit 4. It is clearly a post chapter 3 event... yet everyone seemed to completely accept that Kura was there. It's interesting how they gave you the tools to figure out the anomaly yourself.

I think this is a pretty important event. Trying to forray into the dimension that Cancer draw their power from by connecting to the Cancer's hivemind directly seems pretty dangerous, but this research might actually be essential for victory. The fact that the Cancer just straight up died from it also seems like some kind of failsave? Or maybe it's just that the experiment overloaded it.

Higher dimensional beings are a real mystery at this point, but there have been long standing theories that Cancer are puppetted by such beings. They are just shells after all. The "beach resort" was just a way for Tsukishiro to cope with this incomprehensable higher dimension.

What I don't quite understand is if this Kura in that world is the real one from beyond the afterlife? The finale implies she is being swallowed by the "sanzu river" and she says it will be harder for her to move on when she has the lingering regret of coming with Tsukishiro.
Maybe Mamiya's claim that this is her afterlife where she can live her dream wasn't completely wrong? Maybe these two were actually the real Kura and Mamiya, now higher dimensional beings.

The idea is that Kura, as a higher dimensional being, was manipulating events and she even managed to affect the normal world as shown with the coffee beans raining down at the base, right? Her last apology for acting jealous and interfering with Monaka's reunion with Mamiya... they really are so clumsy at telling each other how they feel.

If nothing else this gave a bit of closure on Mamiya being actually dead and that Monaka's feelings for Kura were greater than for Mamiya.