That day, everything humankind took for granted collapsed into an unspeakably odious hell. First came a storm of wasps whose stings rotted flesh and dissolved bone. Next came the "Dollies"—terrifying doll-like giants with live "human vacuums" and an array of other ghastly weapons at their disposal.

Half a year later, only 1% of the global population remains, and traumatized survivor Iruma Ikaruga reflects on the carnage he witnessed on that tragic day. On the verge of suicide, he inadvertently saves a girl named Yuu Banira from her would-be rapists, and the grateful Banira invites him to join the resistance group Trial and Error.

Iruma reluctantly agrees, and he later witnesses Trial and Error's near-impossible feat of capturing a Dolly. However, the operation falls into shambles when a more powerful and intelligent "Pygmy Doll" appears, killing the captive and wreaking havoc at the location. But despite the slaughter, this encounter between Iruma and Pygmy will prove vital to unraveling the elusive mystery behind the Dollies' purpose and existence.