Eiji, a stoic young hero, completes the 'Trial of Testing' at the Holy Sword Institute, mastering the ultimate sword skill 'Ikken Iten' and earning the title of 'Hao Yuusha' (Supreme Hero). However, he shocks the powerful Institute Director and assembled dignitaries by refusing the 'Hao Seiken Excalibur,' the ultimate Holy Sword, and declaring his immediate departure. Eiji's sole motivation was to acquire all sword skills, not to serve the Institute's political agenda or wield a divine weapon. His new, ambitious goal is to forge a sword with his own hands that surpasses even the Hao Seiken.
Six months later, Eiji is found toiling as the sole human in a small dwarf mining settlement, enduring harsh labor to learn blacksmithing, a skill at which dwarves excel. He resourcefully saves injured dwarves during a cave-in, earning their gratitude but the continued skepticism of Gyariko, the strict 18-year-old supervisor and daughter of Chief Darudoru. Gyariko, initially dismissive of Eiji, is unaware that her father hired Eiji due to an old debt. Darudoru recounts how, five years prior, a human hero saved a young Gyariko from a monster, a story Eiji finds uncomfortable.
Later, Eiji is caught by Gyariko while reluctantly participating in a scheme by senior dwarves to spy on her. Frustrated by his low blacksmithing skill (12), Gyariko reveals her secret: a private workshop where she passionately forges swords, aspiring to create a weapon as magnificent as the Holy Sword that saved her. Recognizing their shared ambition, Eiji confesses his true goal and earnestly asks to become her direct apprentice.
Their conversation is abruptly interrupted by an alarm: an Iron Ant, a monstrous, iron-eating scout, has invaded the mine. Gyariko explains the dire threat: Iron Ants are the "worst of the worst" for mining settlements, as their escape would lead to a swarm destroying the community. Eiji, armed with one of Gyariko's iron swords, confronts it. Though his first strike shatters the blade, leaving only a faint scratch, Eiji proves ordinary weapons can inflict damage. He then systematically uses dozens of Gyariko's carefully crafted swords, breaking each against the monster's shell while precisely striking the same spot. Gyariko, observing his superhuman precision and unyielding spirit, uses her 'Status Appraisal' skill on a broken hilt. To her astonishment, it reveals Eiji's Sword Skill value: an unprecedented 3700, far exceeding the hero's qualification of 1000.
In a climactic battle, Eiji, with his last sword, uses 'Water Breaking Slash' and 'Early Summer Rain Slash' to atomize the Iron Ant's corrosive acid, causing it to drift downwind and dissolve the monster's own shell. He then unleashes 'One-Strike Sever,' cleaving the monster's head and saving the settlement. As the dwarves erupt in cheers, Gyariko, witnessing Eiji's movements perfectly mirror her memory, finally realizes he is the human hero who saved her five years ago.
The next morning, Eiji apologizes for destroying her swords, while Gyariko, overwhelmed with embarrassment and gratitude, now speaks to him with utmost respect. Darudoru confirms he knew Eiji's identity all along. Eiji explains he quit being a hero to forge his own sword, reiterating his plea to Gyariko. Darudoru grants them a day off. As they walk, Eiji convinces Gyariko to drop the formalities, and they acknowledge their shared, albeit not yet fully understood, dream of creating extraordinary swords. However, their peace is short-lived as the Holy Sword Institute's search party for the "missing Sword Master" arrives at the dwarf settlement.
