The world has already ended. The future—where a horrific battle against a parasitic virus called "Gastrea" was fought...and lost. Humanity is cornered and lives in despair. Rentarou and Enju face constant danger in their work as a team of anti-Gastrea specialists known as "civil security officers." As if the daily fight against oblivion weren't enough, they will soon face a threat that could destroy all of Tokyo...