This story focuses on a team of ten parasites part of "Squad 13". Squad 13 is part of an experimental group in Plantation 13. One of them can't be with his partner and he failed the training program. His name is Hiro. He meets Zero Two when his class is doing their graduation ceremony. She is a Franxx pilot that has klaxosaur blood and red horns. She is well known as the "Partner Killer" because many of her partners die. After Zero Two's partner is killed by a klaxosaur, Hiro volunteers to become her new partner.