Nearly half the population of Sakurada, a quiet town near the Pacific Ocean, possesses some form of unique supernatural ability. These powers range from the trivial, such as entering the mind of a cat, to the reality-altering, such as resetting the world back to a previous point in time. To keep these abilities in check, an enigmatic organization known as the Administration Bureau monitors all power use and enforces the town's strict rules.

At the heart of the story are two high school students, Kei Asai and Misora Haruki, who are both members of their school's Service Club, a group that executes missions assigned by the Bureau. Kei possesses a perfect memory, an ability that allows him to recall every detail of everything he has ever experienced. Misora, a seemingly emotionless girl, has the much more drastic power of Reset, which can revert the entire world back to a "save point" she has set, up to three days in the past. The drawback of Reset is that after it is activated, everyone, including Misora herself, loses all memories of the erased period, making the power nearly useless on its own. The key to their partnership is that Kei's memory is immune to Reset; he is the only person who can remember what happened in the time that was erased. Together, they form a perfect team: Misora can rewind time to fix a problem, and Kei can retain the knowledge of the original timeline to guide their actions.

The narrative begins with seemingly simple missions from the Bureau, such as a request to revive a dead cat, which the pair solves by using Reset and Kei's retained knowledge. However, their actions quickly draw them into a much deeper and more complex conflict. Kei is haunted by a past tragedy: two years prior, their friend Sumire Soma, a mysterious girl with the ability to see the future, died under circumstances related to a Reset. Convinced he can undo this loss, Kei embarks on a long-term plan to resurrect her, a goal that brings him into direct opposition with the Administration Bureau and its powerful leader, Masamune Urachi.

As the series progresses, Kei and Misora navigate a series of intricate and philosophical arcs. They clash with other powerful ability users, such as Yoka Murase, who can erase anything she touches, and confront the Bureau's ultimate aim of eradicating all supernatural powers from Sakurada. A central figure is the Witch, an ancient oracle trapped in a solitary confinement room deep beneath the city, whose prophecies guide much of the Bureau's actions. Kei's intelligence is constantly tested as he manipulates dozens of abilities in elaborate schemes to outwit the Bureau, revive Sumire, and ultimately decide the fate of powers in Sakurada. The story builds toward a resolution where Kei must make a definitive choice about the future of the town and its inhabitants, confronting the very nature of memory, will, and happiness.