Ajin Part 1: Shoudou

Both deal with a teenager having an alien power inside him and questioning whether he is is still human after all the unbelievable and regrettable things that happen. They both are supernatural shonen with gore scenes and mystery behind the unknown things that reside inside of them. 

Both anime focus on protagonists who have a special power which makes other humans see them as a threat. We follow these characters as they develop their powers, mature, and try to keep their humanity intact by difficult moral choices. Lots of action and violence in both anime as well. 

Both anime focus on characters who are not 100% human and are suddenly thrust into a kill or be killed situation, with not many options as to who to trust. The characters are also somewhat similar, as they are in a dilemma which side to join. Overall, both have a similar atmosphere and storytelling elements. 

Though the genres are a bit different both anime have great and pretty realistic animation, dark atmosphere, intelligent main characters.And there's a weird villain who lost the sense of humanity.  

Both of these anime contain elements of horror, mystery, and supernatural. In fact dark psychological elements are profound characteristics. Both delve into the realm of the human psyche.  

Both anime focus on main characters whose lives are turned upside down as they discover their supernatural abilities in a deadly accident. From there, the main character is thrust in a kill or be killed situation, where he must struggle for survival as he witnesses the darker side of society. The character development in both anime is somewhat similar, and they both contain a lot of action and violence.