Yoake wo Kou Kemonotachi

This is a world where those referred to as mutants exist. Ai Zetsuze 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...?!

(Source: Hakusensha, translated)