In a ruined future, humanity shelters inside mobile fortress cities called Plantations while engineered child pilots known as Parasites defend them in giant mecha called FranXX against the monstrous klaxosaurs. Hiro, designated Code:016, was a celebrated prodigy until he fell out of sync with his partner and lost his place among the pilots. His path turns when he meets Zero Two, a horned human-klaxosaur hybrid whose partners never survive long, and she invites him to pilot at her side.