Legend says that an evil Dark entity's soul, Gerard, was sealed by the Light entity, Lydia, in a stone governed by two swords: The Light sword and The Dark sword.
Sakura believed the legend to be a total myth until her childhood friend, Hideki, returns to their hometown. Her life turns upside down when she learns that she & other kids hold Lydia's elemental powers, with Hideki bearing a key item: The Light Sword.
Reluctantly, they all set on a venture to understand how they are connected to the legend while uncovering secrets and revealing traumas from the past.