Kaibutsu Taishitsu

This is a "constitution" biased world── One day, people with special constitutions began emerging from within humanity. By this, we include people with vampire and werewolf traits. And with the flow of time, these gradually became the norm and people with special constitutions grew to take up ninety percent of the population. But as society became brimmed with these types of people, the bias towards them grew. Those with a particularly strong constitutions now live out their lives in academic cities provided by the government. When Kazuyoshi, someone with absolutely no special trait, in other words, someone with "Zero Constitution" steps foot in one of these cities, he comes upon a seemingly suspicious and special constitutioner...

(Source: Official site)