"Kemurikusa" is a 12-episode anime series set in a post-apocalyptic world where humanity has largely vanished, and the environment is dominated by mysterious red plants known as Kemurikusa. These plants emit a fog-like substance and are both a source of danger and a potential resource for survival. The story centers on a group of sisters—Rin, Ritsu, and Rina—who live in a desolate, crumbling cityscape. The sisters are not entirely human; they possess mechanical bodies and unique abilities tied to the Kemurikusa. Rin, the youngest, is curious and adventurous, while Ritsu is pragmatic and protective, and Rina is quiet and observant.

The sisters' lives change when they encounter Wakaba, a human boy who appears to have no memory of his past. Wakaba’s arrival introduces new dynamics to their survival, as he possesses knowledge and abilities that differ from theirs. Together, they explore the world, uncovering the secrets of the Kemurikusa and the remnants of human civilization. The Kemurikusa are revealed to be more than just plants; they are sentient entities with their own behaviors and purposes, some of which pose significant threats. The group faces various challenges, including battles with aggressive Kemurikusa and the struggle to find resources like water, which is scarce in their environment.

As the story progresses, the sisters and Wakaba learn more about the origins of the Kemurikusa and the fate of humanity. The narrative delves into themes of survival, family bonds, and the relationship between humans and nature. The sisters’ mechanical nature and their connection to the Kemurikusa are explored, revealing deeper layers to their existence and the world they inhabit. The series balances action, mystery, and emotional moments, culminating in revelations about the true nature of the Kemurikusa and the sisters’ purpose in the world. The story concludes with a resolution that ties together the mysteries of the Kemurikusa and the characters’ journeys, leaving a sense of closure while hinting at the broader implications of their discoveries.