If they're old enough, there were male scavengers, so it was more iffy until we got confirmation that they were girls.
Not really, this is pretty much a one-sex environment, as it was confirmed that unisex environments caused chaos at the first time, so now they only have girls, and has been for a long time.
So I think at least for the scavengers, we can safely assume that they’re all girls until proven otherwise, especially since the author has no intention of adding male scavengers within the narrative.
If you’re really uncertain, they/them is still a choice. It‘s honestly really strange to naturally assume a male when this is 99% girls and the rest is ambiguous gendered avenger ghosts.
Oh, and on top of that, I think due to the translation issues, there are times when both “Kei” and “Kay” are used are used to refer to the anti-returner leader. And there are “avengers” but previously they were also referred to as “vengeful ghost”? Also I think there were more appropriate terms than “subjugation”? I am not sure what the raws say but it would be good to provide some consistency, as there has been some jargon terms provided by the past translators, I think.
Aside from that, great job! Thanks again for taking up the translation of this, and looking forward to the next chapter! Toto-Chan is really on fire!