Sakai Yuji's mundane routine shatters when a girl named Shana, with crimson hair and eyes, abruptly alters his fate. Witnessing a surreal scene on his way home from high school—people frozen in an eerie blaze, a menacing doll-like creature attacking them—Yuji faces imminent death until a cloaked girl wielding a massive sword intervenes. Saved from oblivion, he learns a chilling truth: he's no longer the 'Yuji' he knew. Identified as a 'Torch,' a mere shell of his former self devoured by beings called 'Guze no Tomogara,' Yuji discovers he's a rare 'Mystes,' harboring a precious entity within. As he gazes at the flickering flame within him, the Flame Haze companion reveals his unique destiny, marking the genesis of their enduring battle against otherworldly intruders.