High school sophomore Uesugi Kage has been nursing a crush from a chance encounter long ago, unable to move on from that love at first sight. On New Year's Day, an earthquake damages her boarding house, forcing its demolition and leaving her suddenly homeless. Desperate for a new place, she arranges to meet her landlord, Hōjō, hoping for help finding a new property. Instead of a conventional landlord, she comes face to face with a fragile-looking beauty shrouded in a strange, otherworldly aura—a woman who is, in fact, a thousand-year-old elf. This elf, Shirone, offers Kage a place to stay under her own roof, beginning an unusual cohabitation between a human high school girl and an immortal elf. The story follows their gentle, everyday life in a setting that draws on local Niigata details, and explores the slow-blooming relationship between them. Kage gradually realizes that the childhood first love she has never forgotten was actually Shirone herself, and proposes a trial romantic relationship to help Shirone with research for a novel. As they grow closer, Shirone must confront her own past emotions—including a previous attachment to a legendary eight-hundred-year-old nun—and distinguish those feelings from what she now feels for Kage. The narrative culminates in a third and final volume, where Kage decides to leave and return to her family home, only for the two to reunite at a significant seaside location, finally bringing their love to resolution.