Three episodes in, it still looks great and it remains interesting. Although right now there are more questions than answers.
Spoiler

I know some people will say ‘it’s science fiction, doh’, but somehow, a freaking brain transplant seems to me more unbelievable than a post apocalyptic future where weird monsters roam around. Dunno, it makes me think of the Simpsons Halloween special episodes more than the serious mystery scifi story we had until now. So I have to wonder if the nurse was right, and really, its all… a delusion, and the title of the anime is pointing in part to that. Hell, the first encounter with a maneater that we had, on the previous episode, was also about someone that deluded herself into believing a maneater was his lost son, so you gotta wonder if the author was building a theme with that scene. Not only that, but the circumstances around are a bit suspicious to me (literally all that had a relation with her/him went missing, Robin, the doctor, and the other kids, so call me paranoiac, but I wonder if what we have been told is what really happened, or we have been fed a twisted version of reality).

The doubt I have is that I don’t know if the author intends for the brain transplant to be real and it’s the story’s style to not dig into the details, or it’s the opposite and the details are a clue indicating the brain transplant never happened (like, the doctor didn’t even had a state of the art high tech hospital facilities where I could believe with future tech they are posible, he did it was it seemed a rundown average hospital).

The other alternative is that the brain transplant is real, but it was done with monster-based ‘psychic’ tech. In that case, the previous story could have been a clue in that the monsters really when devour people, they can absorb the victim’s mind/soul, and the doctor used something like that to transfer the minds.

Apart from that, well, a lot of mysteries are open. What was the calamity? What’s the origin of maneaters? What was up with the secret lab with kids, and what relation if any, had with the calamity? Do the children have powers?

At first I thought the lab was some kind of high tech refugee done to protect a few from the ‘calamity’, but when the girl showed the drawings of the monsters, and the monsters are THAT weird (a fish with human hands?), as if they came from a child imagination. So maybe it’s the other way around? Did they trigger the calamity?

Apparently, a new spinoff season of Konosuba just started, according to Crunchyroll.

Hopefully it will be as funny as the first two seasons.