Kiseijuu: Sei no Kakuritsu, Tokyo Ghoul √A Recommendations
What the 2 have in common, both involves the same MC whom where a half of a monster that has given them a significant amount of power to fight their own kind, except in TG the MC is somewhere being with the good guys and bad.
Both anime dealing with monster inside after been infected by "something" supernatural.
Both Main characters change greatly psychologically and mentally after lots of thing happen.
Both have the same horror genre and both MC were posses by some entity who has given them special ability but their humanity is at stake.
This is similar in so many ways it's almost shocking
-they are both half monster
-they become more powerful
-both start to lose there sense of humanity as the story progresses
-both half to deal with enemies along the way