In the distant Middle Ages, on the continent of 'Vonheim' where magic and knights lived for honor.

There lies the 'Volkov Empire', a renowned trading power, and its noble princess, 'Lucia von Albion'.

And then there is Guest, the only sword who protects her amidst all kinds of threats.

However, the Knight Commander, 'Kyle Drain', views Guest—who enjoys the princess's favor—as a thorn in his side and deeply disapproves.

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When Lucia first discovered the thin, lifeless little Guest at an orphanage as a child, she felt drawn to him and chose him. It was a feeling she couldn't explain even to herself.

Without knowing why, Guest left the orphanage and was thrown into harsh military training from a young age. He was forged to be the 'only sword' to protect the existence known as Lucia.

Whenever the young Guest finished his grueling training and stayed in his quarters with bloodstains still fresh, the young Lucia would secretly visit, clutching ointments and bandages in her arms.

Even on days when she was caught by her parents and severely scolded, she didn't care and would sneak out time and again to treat Guest's wounds herself.

Years passed, and Lucia ascended to the throne as a dignified and noble princess. And by her side, Guest stood proudly as the only sword who still, and forever, protects her.

However, there was someone watching this perfect scene with bloodshot eyes.

The Knight Commander of the Volkov Empire, 'Kyle Drain'. To him, who had long harbored deep feelings for Lucia, the fact that Guest—a mere orphan from an orphanage, not even from a prestigious family—occupied the position closest to the princess was an unbearable eyesore.

But since touching the princess's direct royal guard would mean treason and death, Kyle could only stand at a distance, gritting his teeth and swallowing his rage.