Valen was once hailed as the greatest mage of the Gloria Empire, the legitimate heir to the Genova school of magical combat. But in a devastating battle, he lost everything: his beloved master, his eyesight, and the vast majority of his magical power. Now he lives a listless, retired life, barely scraping by as a flute player. His only remaining strength can be unleashed for a mere ten seconds before it fails him entirely. Compounding his troubles, he is hopelessly awkward around women.

That solitary existence is shattered when a young girl named Ria appears before him with a staggering revelation: Valen's master is still alive. Ria is a prodigy overflowing with raw magical talent, and she forces her way into becoming Valen's apprentice, barging into his life like an uninvited wife. To survive on the road as a girl with a male master, she makes a determined choice: she will disguise herself as a boy at all costs, hiding her true gender even at the risk of death. Sensing traces of his lost master within Ria's immense magical potential, Valen reluctantly accepts her as his disciple. Together, the new master and apprentice of the Genova school set out on a journey to find Valen's missing teacher.

Their travels lead them from town to town, following scattered reports and sightings of the master named Gina. As they travel, Ria's overwhelming talent blossoms, and she rapidly masters a wide variety of techniques, much to Valen's quiet pride. But the road is not smooth. A great darkness begins to gnaw at Ria from within, threatening to consume her. Meanwhile, the ancient and destructive Wind Dragon Widorect, once brought to ruin, stirs back to life. A reunion with the grandmaster Gina herself only deepens the mystery, leaving Valen struggling to make sense of her cryptic words. The pair's strange journey, born from a simple search for a lost master, somehow becomes entangled with a chain of events that could lead to the destruction of the human world. At the heart of it all lies a stunning truth: the former strongest mage's cross-dressing apprentice is fated to become the Demon King.