Spiral: Suiri no Kizuna, Shiki Recommendations
In both manga, there are people that aren't allowed to exist because they may be a threat to the others. It is discussed the moral problem of killing a murderer and there are also twists and smart moves. There are complex characters, well psychological analyzed and some of them show their madness and obsessions. While Shiki is a supranatural and horror manga, Spiral is a mystery manga and it also has a more optimistic atmosphere and less gore. However, both express deep feelings and they manage to shock the readers.