 If you liked
Ajin
|
 ...then you might like
Yakusoku no Neverland
|
If you liked Ajin or the Promised Neverland...
You'd enjoy the other. Both are set in a world that has a much darker side to it, the main cast are both struggling to survive in a world they thought they knew.
The people they thought were friends, may or may not still be their friends.
Both anime are complex, have a great pacing to them and contain 'monsters'.