Mira Yoo became the 25th master of the Moon Light Sword Style after her father, whose obsession with their ancestral sword impoverished the family. Trained from childhood, she inherited the heirloom sword on her father's deathbed with the command to revive their martial legacy. This duty defined her youth, leading her to live with her uncle Yu Deuk-Chun and cousin Yu Su-Mi while attending school. During this time, she dated multiple fighters seeking a suitable partner to propagate the sword style, ending relationships when candidates proved inadequate. Though initially presenting a fragile demeanor, her combat skill allowed her to effortlessly defeat groups of delinquents.

She entered the God of High School tournament seeking a worthy husband, but her motivations shifted after befriending Jin Mori and Han Dae-Wi in the preliminaries. Mori challenged her protective stance toward the sword, advising proactive safeguarding over reactive retaliation. This proved pivotal when a manipulative CEO stole her sword during a forced marriage; though devastated, she forgave Mori for failing to retrieve it, releasing her family's expectations. Throughout the tournament, she demonstrated exceptional swordsmanship, placing third regionally behind Mori and Dae-Wi. She defeated opponents like Ma Miseon using swordless techniques and Park Il-Pyo by activating her National Treasure weapon mid-battle, securing formal ownership of the sword.

Her combat capabilities include superhuman strength, speed, agility, and endurance honed through rigorous training. She split mountains, reacted to laser beams, diced arenas into fragments, and endured prolonged battles. Initially reliant on brute force, she later incorporated greater skill. During the Sage Realm conflict, she received Charyeok training from Judge P, manifesting Borrowed Power as Yeo-Po Bong-Seon—a power boosting her physical attributes and pain tolerance while enabling her to summon the crimson horse Toma. Her endurance was tested surviving limit-breaker removal side effects using holy animal tears. She later lost an arm to Priest Ryu, who recognized her Moonlight Sword Style and offered destructive mentorship; she rejected his tutelage but adopted his predatory intensity for self-improvement.

After Ragnarök, she received Ultio R's Original Greed and the Jade Emperor's physical power, recognized as the Emperor's successor. Sang Mandeok acknowledged her authority, and she became leader of Neo Nox—merging the National Assembly of the Homeless with Sang Man-Duk's Nox faction. Seventeen years post-Ragnarök, her skills earned her status as one of The Six, nicknamed the Witch of the West. Empowered by the King's Body, she manipulated fundamental forces like gravity and strong nuclear energy, fought the Jade Emperor repeatedly, and wielded the Blade of Tathagata to pierce the Robe of the Sage. Her strength and speed reached planetary levels, cleaving continents and reacting to condensed projectiles from Sage-empowered opponents. However, conflicting memories from the King's Body fractured her psyche, resulting in emotionless cruelty and a savior complex.

Following Maitreya's advent, she sacrificed the King's Body to save Han Dae-Wi, restoring his arm but losing most divine abilities. Fragments retained in her cells provided limited durability, insufficient against foes like Deer. She later obtained Park Mubong's Right Arm via Project Wi-Fi, combining it with residual King's Body cells to fight the Four Pillars of Fate and defeat Rabbit by activating Original Greed's full power—devouring billions of clones globally. Ultimately, she used Project Wi-Fi to complete Jin Mori's transformation into Maitreya, losing her Charyeok and weapons. Post-conflict, she served as Minister of Defense in Park Ilpyo's world government, married Han Dae-Wi, and raised their son Han Seungtae alongside adopted children. Her Wi-Fi arm was replaced with a standard prosthetic, her injuries healed, and she retained white hair cut to shoulder length.