There is an advanced civilization on the dark side of the moon comprising of two families, the Takenouchi and Umenouchi clans. Leading as acting queen is Takenouchi Fumiya, with her daughter Kaguya as the next heir to the throne. Despite Kaguya's privileged position, she is unsatisfied with the inflexible laws of their society and opposes her mother's reign, giving her a rebellious nature.
Unfortunately, Fumiya is ill with a severe condition that she has hidden from her daughter. Knowing that she cannot conceal it any longer, Fumiya decides to send Kaguya to Earth with an influential katana that signifies their family's control over the moon. Fumiya trusts that this transfer would strengthen Kaguya and help her reclaim what was taken from them by the Umenouchi family.
As the Umenouchi clan relies on the sword for power over the moon, Kaguya must mature and find the strength within herself to regain her rightful inheritance.
