The story follows elven mage Frieren, a former member of the party of adventurers who defeated the Demon King and restored harmony to the world after a ten-year quest. The heroic group includes human hero Himmel, dwarven warrior Eisen, and human priest Heiter. Before they part, they observe the Era Meteors together, a meteor shower that occurs once in fifty years. Frieren agrees to see them again and offers them a better view the next time the celestial event occurs. Frieren then departs and travels the world in pursuit of magical knowledge.
Frieren returns to the capital fifty years later; however, humanity has changed, and her former companions have distinctly aged. After one last adventure to see the meteor shower, Himmel dies of old age. During the funeral, Frieren expresses guilt for not attempting to learn more about him. Paying a visit to her other former comrades, she accepts Heiter’s request to teach and care for Fern, an orphaned child adopted by Heiter. She also receives an invitation to travel far north to the resting place of souls and see Himmel again to bid the hero a fitting farewell and express her feelings. To fulfill those requests, Frieren embarks on a journey together with Fern while still pursuing her passion for learning magic. Along the way, she is joined by Stark, a young warrior boy taught by Eisen.
Frieren’s elven nature grants her an extremely long lifespan, causing her to view periods of years or decades as ephemeral (this perception of time makes her consider the ten-year adventure with Himmel’s party a fleeting experience). The story thus takes place across a long time, with periodic flashbacks accompanied by the physical and mental development of characters apart from Frieren herself.