Emily Carter, a modern farm heiress, is facing property seizure and murder attempts from her greedy uncle Marcus. At her wit's end, she discovers that the farm's old fireplace actually connects to a fantasy kingdom called "Esthelgard." On the other side of the fireplace, the young King Kyle is leading his battered troops to the brink of doom, besieged by the Shadow Witch King Malrick's frost armies.
A bottle of modern medical alcohol cures the king's strange poison; a bag of pure gold coins smashes open the doors of modern arms dealers. Emily becomes a cross-realm arms dealer, continuously sending modern supplies, antibiotics, and even Gatling guns through the fireplace to the other world, helping Kyle turn the tide of battle; while Kyle uses top-grade rubies and magic to protect Emily, helping her smash the attacks of modern assassins.
As the space-time rift expands, the crises of the two worlds begin to intertwine. The fantasy world's extreme conservative faction—the "Hermitage Order" (secretly controlled by the Queen Mother)—joins forces with modern capitalist conglomerate Sterling Group, attempting to completely monopolize the space-time passage. Malrick takes the opportunity to resurrect an ancient dragon, triggering an ice age; while Sterling attempts to weaponize void energy, threatening the entire globe.
Facing the double stranglehold of magic and capital, Emily and Kyle swear a blood oath in desperate circumstances. Emily uses C4 and fuel-air bombs to blast through the conspiracy of the fantasy world, while Kyle uses the Light Origin and ultimate close-combat fighting to cut through the modern conglomerate's private army. In the end, Kyle willingly abandons his demigod magic power to completely seal the void; Emily terminates Sterling's ambitions in the modern world. Having crossed the trials of space-time and life and death, and witnessed by the cheers of ten thousand people and modern allies, Emily is officially crowned Queen of Esthelgard, ushering in a brand-new era for both worlds.