Fuji no Yamai wa Fushi no Yamai.

Without warning, humanity is plunged into a world where the number of diseases has grown exponentially. Although skilled doctors exist, the unfamiliar nature of these illnesses only renders conventional treatment methods useless. However, not all hope is lost when Dr. Ikuru Fujimi is around. Ikuru has a disease unlike any other—it makes him immortal and gives his blood remedial powers, which he exploits to cure his patients. Society finds it difficult to accept his methods, but Ikuru is single-minded on attaining the one thing that is elusive to him: death. With a burning wish to leave the world and his past behind, Ikuru travels to find the disease that can finally grant him the demise he so desires. [Written by MAL Rewrite]