I Learned How to Behave in the Underworld

"Did you know that we have actually been living in the underworld?" Zhang Ling, who was originally just an ordinary college student, felt that the world he had lived in for more than 20 years felt something was not right. A corpse with a hideous appearance? Only legendary ghosts exist? Ding ~ System awakens! Zhang Ling, who thought he could reach the top of his life by relying on the system, never expected that the cheating system would actually shake hands with the monster in front of him who was bleeding from seven holes and covered with pustules on his hands?