Kakeru Dimasupil, a shrewd Manila CEO, meets his untimely end, only to be granted a bizarre second chance: reincarnation in a medieval fantasy world. Reborn as Shouyo, a child in the desolate, bandit-ridden village of Kutsilyo, his past life's strategic brilliance awakens. With it comes Appraisal, the ability to see true potential, and Divine Blueprint, the power to conjure impossible inventions. But this new life is far from the trivial mysteries he once craved; it's a brutal fight for survival.
Kutsilyo is a forgotten realm, exploited by ruthless mercenaries and opportunistic bandit factions. When his gentle older sister, Yui, is brutally murdered in a marketplace raid, Shouyo's quiet ambition transforms into a cold, unyielding thirst for vengeance. He forms the Kutsilyo Shadows, a clandestine group of desperate survivors and newfound loyalists like the nimble Lindsy, his steadfast friend Miles, and the resilient Asuna. Operating from the depths of shadow, they begin a meticulous campaign of sabotage and psychological warfare.
Shouyo orchestrates a brutal gang war, pitting the dominant bandit lord Grimo against the mercenary Captain Valerius. Leveraging Stanley, a rescued noble with invaluable foreign intelligence, and coercing the pragmatic bandit leader Feron into his service, Shouyo's machinations dismantle both oppressive forces. His victory, however, exposes a far grander, more insidious truth: Kutsilyo is not merely a forgotten village, but a strategic nexus of unparalleled value, coveted by powerful noble houses like Blackwood, Thorne, and the arcane-obsessed Volkov.
Realizing his family, the Contis, were once rulers of this land, Shouyo sheds his old name, declaring Kutsilyo the sovereign city-state of Rimuru City, and himself its King. He gathers his loyal ministers, including Elara, the medic, and the ingenious engineers Johnson and Johny, along with the shrewd commerce masters Steve and Marlow. Driven by his Divine Blueprint ability, Rimuru City undergoes a miraculous transformation. Steam technology, mana-infused defenses, and booming industries rise from the ashes, attracting the attention of distant kingdoms. Rimuru defies King Leo Von Delgado, securing vital alliances with powers like the Sunstone Confederacy and the Riverland Commonwealth.
Seven years after its founding, King Leo launches a full-scale invasion, only to be repelled by Rimuru's devastatingly advanced, mana-powered cannons. This stunning defeat shifts the war into the shadows. King Leo, along with the scheming noble houses, unleashes spies and mages to uncover the source of Rimuru's unprecedented power – the "energy fluctuations" they've detected beneath the city.
This leads to a terrifying revelation: the existence of the Heart of the Earth, an ancient, living magical entity dormant beneath Rimuru, directly linked to Shouyo's unique abilities. House Volkov attempts to awaken and harness this primordial power, forcing Shouyo to lead a desperate mountain assault. He stops their immediate threat, but in doing so, unknowingly fully awakens the Heart, forging a profound, often overwhelming, connection with it.
The awakened Heart bestows immense blessings upon Rimuru but also makes the city an unmistakable beacon of power. The noble houses intensify their efforts, with House Valerius launching a chilling new strategy: targeting Shouyo's "closest connections"—his beloved Queen Lindsy, now pregnant with their child, and his loyal ministers. They believe this will sever his link to the Heart.
As the lines between physical war and arcane espionage blur, Shouyo discovers a darker secret within the Heart itself: a vast, subterranean cavern where a colossal, shadowy entity named Aetherius stirs, hinting at an ancient struggle far beyond the ambitions of kings and nobles. Shouyo finds himself at the heart of a millennial conflict, forced to protect his nascent kingdom, his family, and the very soul of his world from forces he barely comprehends.