A few young girls with strange powers and a tree that has grown through a railcar cling onto life in a desolate land, searching for its last reservoirs of water. Their routine struggle to survive is interrupted by the arrival of Wakaba, a boy with no memory beyond his own name.

The girls and their new companion commit to a perilous journey across seas of burning red fog—all in order to find what they need to sustain themselves on the more distant, dangerous islands swarming with robotic bugs. Their ultimate fate will be decided by their own strength, along with Wakaba's curious ability to understand the Kemurikusa: mysterious glowing leaves with wondrous powers. Besides the girls, Wakaba, and the hordes of ravenous bugs, the Kemurikusa are the last sparks of life surviving in this land. How did things end up this way? Why are there so many empty buildings with no one to live in them? Wakaba and the girls lack the answers to these questions, which means the truth can only be found within the Kemurikusa.