Digimon >> Digital Monsters 4 Digimon World

From the introduction: It is a time of great turmoil in the digital world. Not long ago all contact with the Yamato Server, one of the four largest servers in the digital world was lost, and with it almost the entirety of the Digital Security Guard (or DSG for short) who had left en mass to aid the server. Worse still, a Doom Server has risen in its place; a foreboding land filled with abnormally hostile and aggressive Digimon. Captain Leomon was sent along with the expeditionary unit to scout the new server, but they have been lost. His last reports indicated a strange infection designated “The X-Virus” had spread through the server; causing the local digimon to become incredibly hostile.