Yoake wo Kou Kemono-tachi

This is a world where those referred to as mutants exist. Zetsuze Ai is a class 5 mutant who has fallen in love with his human co-worker, Kanzaki. He had given up on the possibility of romance with a normal human, but when he was at the inspection facility for mutants, he saw Kanzaki, someone he never thought would be there and now...?!