After the destruction of their hometown, childhood friends Kafka Hibino and Mina Ashiro make a pact to become officers in the Defense Force—a militarized organization tasked with protecting Japan from colossal monsters known as "kaijuu." Decades later, the 32-year-old Kafka has all but given up on his dreams of heroism. Instead, he cleans up the remains of the slaughtered kaijuu after they are defeated by valiant soldiers—including Mina, who has successfully achieved their shared goal. Upon meeting his new coworker, Reno Ichikawa, Kafka faces a mirror of his past self: an ambitious young man whose one desire is to fight as a member of the Defense Force. Unfortunately, the two are soon involved in a freak encounter with a rogue kaijuu. Though Kafka demonstrates his innate heroic nature and rescues Reno from certain doom, he is left gravely injured. While both men recover in a hospital, Kafka is seemingly attacked by another one of the beasts. As a result, he gains the ability to transform into a humanoid kaijuu with the strength and powers of the massive monsters menacing Japan. Dubbed "Kaijuu No. 8" by the military, Kafka resolves to use his newfound gifts for the greater good. Tied together by mutual respect, Kafka and Reno set out to join warriors like Mina at the forefront of the Defense Force.

Substitute Soul Reaper Ichigo Kurosaki spends his days fighting against Hollows, dangerous evil spirits that threaten Karakura Town. Ichigo carries out his quest with his closest allies: Orihime Inoue, his childhood friend with a talent for healing; Yasutora Sado, his high school classmate with superhuman strength; and Uryuu Ishida, Ichigo's Quincy rival. Ichigo's vigilante routine is disrupted by the sudden appearance of Asguiaro Ebern, a dangerous Arrancar who heralds the return of Yhwach, an ancient Quincy king. Yhwach seeks to reignite the historic blood feud between Soul Reaper and Quincy, and he sets his sights on erasing both the human world and the Soul Society for good. Yhwach launches a two-pronged invasion into both the Soul Society and Hueco Mundo, the home of Hollows and Arrancar. In retaliation, Ichigo and his friends must fight alongside old allies and enemies alike to end Yhwach's campaign of carnage before the world itself comes to an end.

Alto Goldfilled, a diligent student at the Ortigia Academy of Magic, aspires to become a powerful sorcerer. But he is unable to become one as, despite his excellent grades and strong commitment to his studies, he fails his summoning class. With the threat of repeating a year hanging over his head, Alto tries following an old, worn-out grimoire in a desperate attempt to resolve his situation. To his surprise, he succeeds and summons a powerful demon named Vermeil. As a sign of gratitude for releasing her, Vermeil agrees to become Alto's familiar, sealing their relationship with a deep kiss. Little does Alto know what else he is capable of and what Vermeil's past hides.

The rare and inexplicable Puberty Syndrome is thought of as a myth. It is a rare disease which only affects teenagers, and its symptoms are so supernatural that hardly anyone recognizes it as a legitimate occurrence. However, high school student Sakuta Azusagawa knows from personal experience that it is very much real, and happens to be quite prevalent in his school. Mai Sakurajima is a third-year high school student who gained fame in her youth as a child actress, but recently halted her promising career for reasons unknown to the public. With an air of unapproachability, she is well known throughout the school, but none dare interact with her—that is until Sakuta sees her wandering the library in a bunny girl costume. Despite the getup, no one seems to notice her, and after confronting her, he realizes that she is another victim of Puberty Syndrome. As Sakuta tries to help Mai through her predicament, his actions bring him into contact with more girls afflicted with the elusive disease. [Written by MAL Rewrite]