Ash Grim Reaper and Immortal Cat

The maritime nation "Republic of Enetia" where the plague "black disease" has begun to spread. In this country, there was a "state affairs assassin" who executed a felony, commonly known as an assassin of justice. Gatto inspires to become a great state-approved assassin. One day, while he is scolded for failing to neutralize a target, his colleague gets killed and turned into a puppet in front of his very eyes... This event leads him to meet a strange individual that claims they are a god of death.