The world of Lingalind is surrounded by a mystical wall with seemingly nothing beyond its confines. Worshipped as the mother of the land, the wall delivers celestial gift capsules called Rakuho'' to locations across the continent. Arriving once a month, the capsules contain metallic armbands that allow the wearer to transform into a mechanical being known as a Briheight. As a result, Lingalind is thrown into constant turmoil by its warring nations, all hoping to strengthen their military prowess by procuring the offerings for themselves. One day, a Rakuho crash-lands in the countryside with an unexpected inhabitant—a mysterious black-haired man. All eyes are set on this strange newcomer, who calls himself Back Arrow, when he claims to have hailed from a place beyond the wall—a revelation that can potentially unravel Lingalind's entire dogmatic foundation.

According to legend, Beelzebub, one of the seven princes of Hell, betrayed God and was banished from Heaven for eternity. Beelzebub now leads the kingdom of Pandemonium, where all former angels roam and work every single day of their immortal lives. A devil like him would give people chills at the mere mention of his name. But what if Beelzebub is not as evil as initially thought? What if he was obsessed with fluffy things? And what if Beelzebub is actually a woman? That is what new assistant Myurin discovers when he is hired to serve Her Majesty Beelzebub. She may know exactly what to do to keep Pandemonium running like clockwork, but whenever she leaves the professionalism of the office, the girl needs some assistance in order to function like a normal... devil. As much as Myurin can't stand being unprofessional, he is secretly obsessed with her adorable antics, and his new job teaches him that everything is not exactly what it seems, especially with the other head devils of Pandemonium.

Mayumi Doujima promises her parents that she will give up on her dreams of becoming an astronaut on her 14th birthday if she cannot find a star she once saw long ago. Overhearing her troubles, the eccentric Manabu Soutouin offers to help her search for the star alongside the rest of Yubiwa Academy's mysterious Pretty Boy Detective Club, whose rules are as follows: Be pretty, be a boy, and be a detective! However, Mayumi is unique—she can see many things that ordinary people cannot. Her eyesight allows her to see the tiniest of details, from people approaching her at a distance to hidden traps that would otherwise go undetected. When the search for the lost star begins to sour, the Pretty Boy Detective Club end up entangled in something far beyond what they ever imagined.

In the distant future, humanity has been driven to near-extinction by giant beasts known as Klaxosaurs, forcing the surviving humans to take refuge in massive fortress cities called Plantations. Children raised here are trained to pilot giant mechas known as FranXX—the only weapons known to be effective against the Klaxosaurs—in boy-girl pairs. Bred for the sole purpose of piloting these machines, these children know nothing of the outside world and are only able to prove their existence by defending their race. Hiro, an aspiring FranXX pilot, has lost his motivation and self-confidence after failing an aptitude test. Skipping out on his class' graduation ceremony, Hiro retreats to a forest lake, where he encounters a mysterious girl with two horns growing out of her head. She introduces herself by her codename Zero Two, which is known to belong to an infamous FranXX pilot known as the Partner Killer. Before Hiro can digest the encounter, the Plantation is rocked by a sudden Klaxosaur attack. Zero Two engages the creature in her FranXX, but it is heavily damaged in the skirmish and crashes near Hiro. Finding her partner dead, Zero Two invites Hiro to pilot the mecha with her, and the duo easily defeats the Klaxosaur in the ensuing fight. With a new partner by his side, Hiro has been given a chance at redemption for his past failures, but at what cost?