Mahiru and Kuro

The story revolves around a 16-year-old boy named Mahiru Shirota who likes simple things and dislikes difficult things. One day, he picks up a stray black cat he finds in the middle of the road and names it Kuro. From this moment on, a contract between the Servamp Sleepy Ash - "Kuro" and Mahiru are formed. Mahiru is pulled into a servamp war between the Servamps, representing the seven deadly sins, and their eighth sibling Tsubaki.