The story takes place in Japan. The year is 2030 and Earth has been completely overrun by a viral disease named "Gibia" that turns infected people into various different monsters, based on their age, sex, and race. A samurai and a ninja from the early Edo period travel together through time and arrive in a ruined Japan to aid a professor working on a cure for the virus. Together, they fight countless Gibia monsters, outlaws, and other fierce foes on their journey to save mankind.

Ever since she was young, Haruka Haruno has always aspired to become a princess. Despite being mocked for this seemingly childish wish, Haruka perseveres to make her dream a reality, ultimately culminating in her acceptance into the prestigious Noble Academy—the birthplace of people's fantasies. When Haruka arrives at her new school, a chance encounter with a pair of magical creatures influences a series of unbelievable events, and Haruka awakens as "Cure Flora," the princess of blooming flowers. After two of Haruka's classmates also transform into legendary princesses, a story of self-discovery unfolds as the newfound team "Princess Precure" carries the responsibility of protecting everyone's dreams. Engaged in a battle between hope and despair, Haruka may find the key toward becoming the princess she has always dreamed to be. [Written by MAL Rewrite]

The year is 2071. Humanity has been pushed to the brink of extinction following the emergence of man-eating monsters called "Aragami" that boast an immunity to conventional weaponry. They ravaged the land, consuming almost everything in their path and leaving nothing in their wake. To combat them, an organization named Fenrir was formed as a last-ditch effort to save humanity through the use of "God Eaters"—special humans infused with Oracle cells, allowing them to wield the God Arc, the only known weapon capable of killing an Aragami. One such God Eater is Lenka Utsugi, a New-Type whose God Arc takes the form of both blade and gun. Now, as one of Fenrir's greatest weapons, Lenka must master his God Arc if he is to fulfill his desire of wiping out the Aragami once and for all. The monsters continue to be born en masse while the remnants of humanity struggle to survive the night. Only God Eaters stand between the Aragami and complete and total annihilation of the human race. [Written by MAL Rewrite]

The story is set in modern times, but the twist to the story is that Mazinger is an ancient weapon of the gods, left on earth to battle the evil space gods who have returned to take over the universe.