It is 972 A.D., the middle of Heian Era in ancient Japan. Kyoto, the capital of the country, is suffering serious famine and widespread disease. But to make the chaotic situation even worse, samurai and onmyoji are continuing their selfish strife for supremacy of political power. Unable to overlook the calamity any longer, the Imperial Court orders Raiko Minamoto, a samurai well-known for his archery skills, to seek out a legendary gem said to hold mysterious power to save the world. But Raiko himself also falls ill. So instead, the youngest daughter in the Minamoto family, Hikaru, disguised as a samurai and pretending to be her brother, departs on a long journey in a quest for the gem. Together with her faithful bodyguard, Tsuna Watanabe, she finds herself caught up in many adventures, acquiring companions who join her for the quest. She encounters a handsome sarugakushi named Mansairaku and also an enigmatic onmyoji, Seimei Abe, and experiences countless unpredictable incidents. Hiding her feelings toward Mansairaku, Hikaru gradually gets involved in a great battle.