In the year 199X, the world was demolished with a bombardment of missiles, and the survivors of the cataclysm were forced to live in shelters. It's now the year 2036, and two friends are playing a video game called 'Devil Busters' in the Keihin shelter No. 3. Shortly after they beat the first boss, they unseal Pazuzu. The demon gives them the Demon Summoning Program in hopes of using it for the defeat of Bael along with a warning of a coming menace. Demons then begin to raid the shelter and the two friends must save the remains of humanity.