It's pretty obvious. It's not the first manga doing this kind of dehumanizing scthick, maybe not as obvious as "go eat them", but this kind of theme has been around for ages.
Which is based on freak incidents the us army did very poor immediate self policing work on. like the Ehime Maru.
Public outrage following these incidents did lead to fairly severe consequences for the military involved and legal battles led to retributions being paid by the us govt... and internal changes which is big considering how much cuntery americans generally get away with.
It's "strangers" in general as it blankets multiple societal problems and blames it on ONE group.
japanese conservative xenophobia is quite robust, given they clearly rather run their demographics into the ground than allow changes.
What's clear is that we have a big bad ugly awfull stranger trope driving the aliens design.
they havent been given a single redeeming trait to a comical degree.
Basically wuxia tier evil baddies.
let's see how this thing pans out... it could be good, it could be racist trash.