During the Heian Period of Japan's history, dark spirits still dwelled in the forests, mountains and rivers. Disguised as a male warrior a young woman named Kaidohmaru, 'The Knight of Fire', wages constant war against these forces of evil to maintain the safety of the people of Kyoto. She is allied with three other military knights under the command of charismatic general Raikoh to whom she is hopelessly attracted but vexed by the secret of her gender.

Kaidohmaru's evil opposite is the princess Ouni-Hime, cursed by a malevolent deity and committed to chaos. As a child she and Kaidohmaru played together, as adufts though, Ouni-Hime is so jealous of Kaidohmaru's friendship with Raikoh that she would destroy both of them and the entire capital rather than see the pair united. Trials of honour, sacrifice and sudden death stalk the lives of the protector knights. Emotion is a luxury they can ill afford and romance may just be their downfall when faced with the ultimate enemy.