Suzuko, a high school student haunted by fragmented memories of a childhood fire trauma, navigates a fractured existence between eras. After being discovered as an amnesiac child clutching a small bell and adopted into a contemporary Japanese family, her life fractures further during a gas explosion while escorting neighbor Shūhei home. The blast propels her to the Sengoku period’s battlefields, where village guardian Shukumaru rescues her.

In this past life, clues surface: a shirt matching Shūhei’s modern attire and gradual revelations of her dual identity as Suzu, Shukumaru’s long-lost sister who vanished during a raid only to reappear decades later as an infant. Torn between emerging romantic feelings for Shukumaru and their assumed sibling bond, Suzuko’s resolve is tested when she shields him from flames, triggering another temporal shift.

Returning to the modern era, Suzuko tends to Shukumaru’s wounds and discovers his appendectomy scar—identical to Shūhei’s. This confirms Shukumaru is the adult Shūhei, displaced a decade earlier by the same explosion and raised in the past under a new name. The revelation dissolves ethical barriers, freeing her suppressed emotions.

As a "fire tripper," Suzuko masters her ability to traverse timelines through combustion-linked crises. This power bridges her identities, culminating in her choice to abandon modernity for the Sengoku period. Her transformation—marked by adopting historical garments and severing ties to her adoptive era—signals acceptance of her entwined fates, closing the loop between flame-scarred past and self-determined future.