Digimon World 4 is set in the Digital World, where the Digital Security Guard (DSG) protects the Digital World from threats. You play as a member of the DSG—specifically, a rookie Digimon called to investigate a mysterious digital disturbance.

The game begins with a catastrophic system error that compromises the Digital World’s network. A strange virus-like entity has corrupted data and opened portals to dangerous areas. Your mission is to investigate the source, eliminate threats, and stop the chaos spreading through the network. The deeper you go, the more you learn about the dark force behind the invasion: a mysterious being called Lucemon, a fallen angel Digimon who aims to dominate both the Digital and Real Worlds.