In a world of adventurers and magic lies Naral Island. Every generation, a Demon Lord rises to plague the land, and every generation, a Hero is born to subdue him. For countless centuries, the cycle has repeated with no end in sight. The latest Hero, Juulia "Yusha" Charldetto, has almost completed her valiant campaign alongside her party members: responsible priest Seiran "Seira" Élénoir, enigmatic mage Meiza "Mei" Endust, and hyper-energetic warrior Fai Fai. In the final battle against the Demon Lord, Yusha's party attempt a risky spell to cast their enemy into the drifts of time. But the incantation goes awry, sending Yusha and her friends back to a time before the Demon Lord, before Yusha becomes the Hero, and before the party had even graduated as adventurers. With their memories of the future erased, the four girls restart their ambitions to become the Hero's Party, aspiring to defeat the Demon Lord. However, in a sudden twist of fate, the Demon Lord was also sent back in time with her memories intact. Reduced to the form of a little girl, the Demon Lord takes the name Mao and infiltrates the adventurers' school as a teacher, planning to stop Yusha before she becomes a hero. Thus begins the story of Yusha and her friends, in their quest to defeat the Demon Lord, not knowing that the one they seek is right by their side.

Five separate worlds—Black, White, Green, Red, and Blue—are linked by the "Halo" and exist in a harmonious balance. However, the Halo suddenly opens in an event known as the World Connect, threatening to destroy the universe. Coming under attack by Ouroboros, an alien species that wishes to accelerate the universe's end, the five worlds recruit girls with special abilities called Exceed to defend against them. Saya Sougetsu, a young girl from the Blue World of Earth, is one such individual able to wield Exceed power. Believing this to be her chance to make a difference, Saya eagerly joins the defense force. There, she meets Amane Ayashiro, another girl from Earth, as well as a selection of fighters from the other worlds. Faced with a formidable foe, the girls must prove that their newfound bonds are strong enough to save the future.

Serval and Caracal find a "human" child in the forest. As they travel with the child, they meet new Friends, uncover the secrets of Japari Park, and become involved in an event that will "shake the earth." (Source: ANN)