At the end of the twenty-first century, a rare disease named "Cagaster" began infecting the human race — transforming them into massive insects. Two-thirds of Earth's population had been devoured by these insects before humanity came to a decision: those that were infected must be exterminated.

In the year 2125 — thirty years after the discovery of Cagaster — a young exterminator named Kidou finds a man dying from insect-inflicted wounds at the edge of the desert near the insects' "cage". The dying man entrusts Kidou with his daughter, Ilie, and tells him to seek out the girl's mother.

Self-published on Hashimoto-sensei's website from 2005-2013 until in 2015, Tokuma Shoten picked it up for publication.