Yuji Sakai is about to learn that there is more to the world than going to school and finding a girlfriend when he meets a sword-wielding girl with fiery red eyes and flame-colored hair. Denizens of the Crimson Realm are invading our world and it's up to the Flame Haze, Shana, to slay them. However, when Yuji gets in the way of her sword, he learns that death is very different from how he imagined it would be.

Yuji Sakai is about to learn that there is more to the world than going to school and finding a girl friend when he meets a sword-wielding girl with fiery red eyes and flame colored hair. Denizens of the Crimson Realm are invading our world and it's up to the Flame Haze, Shana, to slay them. However, when Yuji gets in the way of her sword, he learns that death is much more different than he imagined it would be. Yuji and Shana must work together to fight the Denizens of the Crimson World and learn more about each other and the worlds they are from.

Yuji Sakai is beginning what he thinks will be another boring year of school. But everything changes when the world around him stops, the surrounding people are engulfed in blue flames, and a freakish doll-like creature begins sucking them up! Before Yuji suffers the same fate, a young redheaded girl with a sword appears and saves him. Yuji is drawn into the struggle between these creatures from another world: the Crimson Denizens and the girl Shana, called Flame Haze.

Yuji struggles to understand the strange world he has been thrust into, his relationship with Shana, and his own mortality. Shana, conversely, tries to adapt to the human world while protecting Yuji, the treasured Mistes.

Friagne abducts Yuji as a decoy to get at Shana, and as a Flame Haze, Shana has no choice but to come to the rescue. Will she foil Friagne's plan to activate the Devourer of the City? Or is it the end for Shana and Yuji?

There's a sinister new Flame Haze in town by the name of Margery Daw, and soon she and Shana are in a fight to the death! Meanwhile Yuji runs into a strange old man named Lamies... who reveals himself to be a most unusual Crimson Denizen indeed.

Lamies the Corpse Collector offers Yuji some advice about his strange relationship with Shana. But Yuji had better act fast if he wants to confess his true feelings, because Shana is trapped in a losing battle with the vicious Margery Daw! Who is Shana's worst enemy: the Crimson Denizens or the Flame Haze themselves?

Invaders from the Crimson Realm have come to Earth looking for something called the Power of Existence. Whoever possesses this profound power will control the very quintessence of reality. To the rescue comes an enigmatic young girl with fire blazing in her eyes. She may be cute and petite, but she's endowed with enough preternatural strength to save the entire universe. Plus, she's got a really big sword!

With Shana and Alastor by his side day and night, young Yuji is learning more and more about his new-found fate. He possesses a one-of-a-kind treasure and has quickly become the No. 1 target for power-hungry freaks from the Crimson Realm. He's even captured the attention of a second Flame Haze. There's only room in Yuji's life for one protective angel... if he's not careful, he might get burned by friendly fire!