The narrative picks up with the protagonist, a former sage named Dwite, and the Hero, Claire, standing on the edge of a cliff overlooking a valley filled with miasma. They are surrounded by a hostile crowd throwing stones and hurling insults, accusing them of betraying the world and plotting to become the next Demon Lords after defeating the previous one. Dwite, bound by magic-sealing shackles, feels utterly powerless, a stark contrast to his past reputation. The Prime Minister reads a decree, denouncing the heroes and ordering their banishment to the Valley of the Dead. Dwite protests, claiming it's a conspiracy, but his pleas are drowned out by the mob's renewed fury, fueled by the King's condemnation.
Claire, despite being wounded by a stone, refuses to flee, believing her sacrifice will bring peace. She tells Dwite he should have escaped alone, as he would have been feared. Dwite, heartbroken, apologizes for involving her and thanks her for standing by him. As the Prime Minister orders the execution, both Dwite and Claire are struck by arrows, falling into the valley.
Dwite awakens at the bottom of the valley, embracing Claire's skeletal remains. Time has lost meaning, and he has become an immortal being, surrounded by the skeletons of those previously cast into the valley. He grapples with his existence and the injustice of their fate. Through prolonged contemplation, he realizes the world itself is flawed, not Claire. He resolves to inherit Claire's desire for peace but through a different, more forceful method. His immediate goal becomes revenge against those who wronged them.
Dwite begins to absorb the miasma, transforming into a powerful undead being, surpassing even the former Demon Lord. He gains the ability to create and control skeletons. He wraps Claire's remains in cloth and uses his newfound power to create a staircase of skeletons to ascend from the valley. Upon reaching the surface, he encounters soldiers guarding a fort. He easily defeats them, his power overwhelming. He then marches towards the capital with his growing army of undead.
Upon reaching the capital, Dwite unleashes a powerful fire magic, destroying the main gate and sowing chaos. He demonstrates immense magical power, far exceeding his former abilities. He then leads his undead horde into the city, overwhelming the panicked populace and soldiers. He systematically conquers the capital, turning fallen soldiers into ghouls and expanding his army. He proceeds to the royal castle, easily defeating the guards and knights, and confronts the King.
Dwite reveals his identity to the King, who confesses to orchestrating their downfall for self-preservation, fearing their power after the Demon Lord's defeat. The King is then devoured by ghouls. Dwite takes the King's crown and Claire's sword, a memento of their past. He establishes his rule over the capital, transforming it into a desolate, miasma-filled land.
Dwite, now a self-proclaimed Demon Lord, begins to build his power. He synthesizes his undead forces to create a powerful subordinate, a monstrous skeletal creature named Grom, who possesses a strong will and serves him loyally. He also forms an alliance with Luciana, a former general of the previous Demon Lord's army, who leads a faction of demons. Together, they plan to conquer the surrounding nations, aiming to create a world of "true peace" through perpetual fear and the suppression of human conflict.
The narrative then details their military campaigns. Dwite, with Grom and Luciana by his side, leads his forces in conquering the kingdom, systematically destroying resistance and absorbing the fallen into his undead army. They engage in battles against human armies, including a significant confrontation with a small nation that attempts to reclaim territory. Dwite's power grows, and he solidifies his position as the new Demon Lord, aiming to impose his vision of peace upon the world. The story concludes with Dwite and his subordinates planning their next moves, with the ultimate goal of establishing a world order dictated by his will, where humanity is kept in check by the constant threat of his power.
