Ambrosia - Who is The MC? AWITM

In a world where all types of characters from different types of stories (Fantasy, Romance, Sports, etc.) coexist peacefully, a detective and his assistant hunt down the most dangerous form of existence: the main characters.
they investigate to find other main characters in the plot of the story, supposed to be a threat to everyone. Their investigation revolves around different themes (basketball game, investigation of a murder, etc. strange phenomena occur during the story (the protagonist is aware of certain words of the narrator, the narrator himself seems to have an influence on the story, and a mysterious character who observes and acts in a certain way behind every event).
Between the mystery of the MCs, the actions of an anti-MC task force, and the identity of the mastermind and its true objectives, the detective will seek to unravel the secret of this world.