>>759408
>Their entire world is doomed and there's nothing anybody can do. What's the point of going on?
There isn't nothing anybody can do. Everything may be doomed, but the heroes fight to make sure that that doom doesn't come yet and that everyone can live as happily as they can for as long as they can, because that's the only thing left they can do.
Blackpill isn't just the situation, but the outlook in response to it. Tougou's reaction was blackpill, but the others, and eventually she too, decided that the only choice was to fight against their inevitable fate and make sure that even if it had to come, it wouldn't come yet, and it wouldn't come easily.
>>759419
>Does the new series take place in an alternate dimension?
No, the first half was a prequel, and the new stuff that's coming up is a direct sequel.
>I didn't realize it got that blackpilled
How far did you get, then? The mankai disabilities are permanent, the cost of the power it gives you. The hero's role is to sacrifice their body in fighting to protect everyone, until they lose so much they can no longer fight, after which they spend the rest of their days immobile and almost insensate, yet unable to die. Tougou nearly met this fate before (in the prequels), but after losing her legs and memory she was placed with a new team of prospective heroes, to begin the fight all over again.
The world is gone. Only the area enclosed by that wall is left, with everything outside the illusory barrier essentially being hell. There, every Vertex they defeat or drive back is endlessly rebuilt and repaired. Victory is impossible, only delay or defeat.
When Tougou learns this, she goes full blackpill and tries to end the wretched world herself, but eventually Yuuna fists her back to her senses, and they stop the Vertexes she let in. At the end, the Divine Tree restores what they lost to mankais, including Tougou's legs and Nogi and Karin's everything.