Weird Fairy? Blood Fairy? Madman?

The protagonist died suddenly in his own world because he stayed up late to answer questions, and traveled to a terrifying world ruled by a group of ghosts. Under the rule of these ghosts, people lived worse than pigs and dogs, and even the phenomenon of cannibalism was just common sense. The protagonist, who had nine years of compulsory education, saw the state of the world and decided to kill the ghost rulers of this world and liberate all mankind to change the appearance of the world. Unexpectedly, the system from the sky came to help him and start his journey to kill gods.