Basara takes place in Japan, about 300 years from a large disaster that occurred around now; the 1990s or soon after. After the disaster humanity and civilization crumbled, and Japan, as an island country, fell into isolation and disrepair. The climate changed, and some parts were turned into desert, while others were filled with all sorts of strange creatures. But at the start of the manga, we are not sure which parts of Japan have been changed, and how, except for where the main character, a girl named Sarasa, grew up. That part, Hyakko village, just north of Shikoku, had been turned to desert, and that is where the story begins. Sarasa is the twin sister of a boy named Tatara, who was prophesied to be the one to lead all out of submission. The submission written of is that of the cruel kings who war against each other for control of Japan; each control a sector of it, but none have yet been able to reign supreme. One of them, The Red King, learns of this prophecy and sends an army to exterminate the village. This is where the story begins.
Descriptions taken from AniDB.net