Zankyou no Terror, Inuyashiki Recommendations
Both series are mature in tone and tackle morality, terrorism, and what it means to be human. They are set in modern Japan and feature more realistic styles of animation, but they also have a slight sci-fi element: in Inuyashiki, humans gain robotic abilities through an unexplained alien encounter, and in Zankyou no Terror, children are experimented on to make them genius savants. Both series have some very dramatic and emotional moments, too!
Both have similar tone and feature terrorism from the antagonist's perspective.
Both take a twist on the concept of Terrorism, with both having teenage.... characters. Neither have set protagonist or antagonists and really tug at the heart strings as you truly get to know the characters.
Basically, both animes bring up moral questions, both are not apelative in any way and both have excellent script/general history development. Putting minor issues aside, if you enjoyed one, certainly will enjoy the other.
Both have a similar tone and feature terrorism. Both show two opposing sides of a conflict And feature anti-heroes. The characters in both series share a lot of similarities.