Sweating_Cloud
For some reason this scenario reminds of the manga, now anime, The Promised Neverland. After reading the summary we can tell that something is obviously wrong, but the whole "never been attacked" part and the people who "never return" part, made me think of that manga. The whole situation seems too good to be true. Like, this city is under the control of the "demons" and purposefully rears geniuses for the demons to eat/exploit as slaves or something like that. Honestly, it's probably me over thinking though (and thinking everything in terms of anime/manga lol).