The Undead Calamity Begins with a Graveyard Demon

It all begins when Gu Su buys a bootleg version of a Graveyard Demon! If you don't want to die in the game, you must find a way to fight for your life! Scavenging, battling, developing the city; in the end, an Undead Calamity-level existence appears in this world where game and reality merge! — Description from novelcodex.org