Seiya Kanie, a smart and extremely narcissistic high school student, believes that the beautiful but reserved Isuzu Sento has invited him on a date at an amusement park called Amagi Brilliant Park. Much to his chagrin, not only is the location a run-down facility, the supposed date is merely a recruitment tour where Sento and Princess Latifa Fleuranza, the owner of the theme park, ask him to become the park's new manager. Their cause for desperation? As stipulated in a land-use contract, Amagi has less than three months to meet a quota of 500,000 guests, or the park will be closed for good and the land redeveloped by a greedy real-estate company. Seiya is won over by the revelation that Amagi is no ordinary amusement park; many of its employees are Maple Landers—mysterious magical beings who live in the human world and are nourished by the energy created by people having fun. Entrusted with the hopes and dreams of this far-off enchanted land, Seiya must now use his many skills to bring Amagi back on its feet, or watch it crumble before his eyes.

Meet Plug, an unusual girl from a parallel world. Plug is a "Juuden-chan," capable of "recharging" people down on their luck, spreading good cheer wherever she goes!

In a dark void known as the Lightless Realm, a group of children meet and bond, but are then separated and returned to their own dimension. Years later, these children reunite to fight "Admonitions," monsters that originate from the same void, using robots known as "Vess." However, their efforts only slow the ever-encroaching and expanding Lightless Realm from infecting their world. Their lives take a drastic turn when a new foe appears in the form of a "Corpse," whose song is rumored to kill any who hear it within nine days. The "Corpse Song" is heard by the group, and with this, they each begin to pull away and become caught up in their own personal problems—ultimately threatening the fate of humanity.

Waking up in a strange bedroom in a dream world, teenager Haruto Tsukishiro finds a strange app on his phone. When he activates the program, an odd woman appears and tries to drag him to her realm. Luckily, a mysterious, white-haired girl severs their connection and helps him escape, revealing that the woman is a witch; however, their conversation is cut short. As Haruto enters the realm again, he meets an anthropomorphic, talking cat named Katsumi Kanzaki. While the witch's minions pursue them, the white-haired girl opens a door for them to escape. After their ordeal, Haruto describes their savior—which only he can see—and Katsumi, the leading authority on dream world research, realizes that she must be "Lily," a being that resurfaces repeatedly across multiple dreamscapes. Hoping to leave the dream world through a blue door, they enter the witch's realm once again. Finding themselves in peril, Lily reveals the truth to Haruto: witches suffer from "Sleeping Beauty Syndrome," a coma-like sleep state induced by torment in their real world lives. Thus, they cannot wake until they are defeated in the dream world. After finally defeating the witch and locating the blue door, Haruto and Katsumi say their farewells, promising to meet up in the real world. However, when Haruto exits through the door, he awakens in the dream world bedroom once more. Seeking answers, Haruto and Katsumi try to uncover the mysteries of the witches, Lily, and Haruto's own inability to leave the dream world.