The art of sword-fighting is practiced by two tribes: the Tribe of Light, comprised of humans dwelling on the world’s surface, and the Tribe of Shadow, consisting largely of part-human, part-animal or monster beings who inhabit an underground city and appear to age at half the normal rate of the Light tribe. These two tribes coexisted in peace and harmony, their territories divided by the “Words Worth” tablet—a massive monolith slab erected by a guardian spirit. Although the tablet bears inscriptions, neither tribe is able to read the text. One day, Words Worth was mysteriously destroyed by an unknown entity, with its fragments scattered throughout the domain of the Tribe of Shadow. The two tribes blamed one another for the tablet’s destruction, sparking a war that has continued for 100 years. Astral, prince of the Tribe of Shadow, wishes to become a Swordsman of Shadow, but his father, King Wortoshika, forbids him from doing so. He is engaged to Sharon, a beautiful swordswoman who generally likes Astral but wishes he were stronger.