In a far-off future, monstrous creatures called Klaxosaurs have nearly wiped out humanity, pushing the survivors into large fortress cities known as Plantations. Here, children are trained from a young age to pilot giant robots known as FranXX, which are the only known defense against the Klaxosaurs. These kids, raised solely for the purpose of piloting these mechas, pair up in boy-girl teams and have no knowledge of the world outside their city walls. Their existence is validated only through their ability to protect humanity.
Hiro, a young pilot trainee, loses his drive and self-esteem after failing a critical test. Opting out of his class’s graduation, he wanders off to a secluded forest lake. It’s here that Hiro meets an enigmatic girl with horns, who goes by the codename Zero Two. She has a notorious reputation as the “Partner Killer,” a reference to her dangerous track record in the FranXX. As they talk, their Plantation suffers a sudden attack by a Klaxosaur. Zero Two confronts the beast with her FranXX, but the battle leaves her mecha wrecked and her partner dead. In the heat of the moment, Zero Two asks Hiro to join her as her new co-pilot. Together, they manage to take down the Klaxosaur.
With Zero Two at his side, Hiro finds a new opportunity to overcome his previous failures, but he must consider the risks involved.
[Adapted from MAL]