Mutants have popped up in Tokyo. These mutants are the relatives of gods and upon consuming human blood they transform into their awakened state which resembles the god that they are related to. Hachi has a nose as good as any dog's. After his best friend is attacked by a mutant he drinks her blood in order to save her.

(Source: Population GO)

Included one-shot:
Volume 3: Himitsu no Yami