Velenrot

The story is set in Heavenly Host Elementary School, an elementary school that was torn down following the murders and disappearances of several of its staff and students. By the start of the story, another school called Kisaragi Academy has been built over the elementary school site.

In an attempt to colonize Mars, 21st century scientists tasked with terraforming the planet seed it with a modified algae to absorb sunlight and purify the atmosphere, and cockroaches whose corpses spread the algae across the planet as they feed. Five hundred years later, the first manned ship to Mars lands and its six crew members are attacked by giant mutated humanoid cockroaches with incredible physical strength, later labeled "Terraformars"; the crew is wiped out after sending a warning back to Earth.