The war between humans and monsters ended when the hero Gilac defeated the Demon King Ryley. In the years of uneasy peace that followed, Gilac's son, Stan, carries the weight of his father's legacy despite possessing almost no magical power at all. He is a gentle young man who feels deeply frustrated by his inability to help others through strength. When Heim, the former commander of the Demon King's army and his father's close friend, invites Stan to live in a special town, Stan agrees and moves there with his loyal, kind-hearted maid Myra.

The town was originally conceived by Gilac as a place where humans and monsters could coexist, and Heim has been struggling to bring that vision to life. Upon arrival, Stan quickly identifies a core problem: many monsters have left the town because they have no meaningful roles or livelihoods there. Using his open-mindedness and insight, he deduces that the monsters simply need work that suits their natural abilities. He convinces Heim to let him start a job placement service for monsters, matching each one to a career that fits their unique traits. A giant spider becomes a tailor, a vampire takes up blood testing, and an orc finds work suited to its physical strength. The human and monster residents begin to thrive together as the town grows more prosperous.

Stan's younger brother, Fleur, arrives from the kingdom of Bayemondo. Unlike Stan, Fleur inherited all of their father's combat prowess and is a talented knight who harbors deep suspicion toward monsters. He initially distrusts Heim and worries about Stan's safety. However, after witnessing the peaceful coexistence firsthand, Fleur gradually softens and comes to support his brother's mission.

The peaceful progress is threatened when Wilbur, a former high-ranking officer under Heim who now leads a reclusive monster community called the Dark Abyss Empire, confronts Stan. Wilbur demands that Heim be freed, claiming that the elf commander is being imprisoned against his will. To explain his demand, Wilbur reveals the hidden history of the war. The Demon King Ryley was originally a gentle human who loved animals. After a cruel hunter killed his beloved beast and bragged about it, Ryley's heart twisted with hatred. He allied with Heim and used the monsters to wage war on humanity, believing that if the weak are always preyed upon by the strong, then the strongest species—humans—must be eliminated. When Gilac confronted him, the hero refused to simply kill the Demon King. Instead, he saw that many monsters were being controlled through mind magic. Gilac freed them, guaranteed their safety, and pleaded with Ryley to choose coexistence over destruction. Moved by Gilac's words, Ryley decided that only his own death could truly end the war. He entrusted Gilac and Heim with the mission of building a world where humans and monsters could live together in peace.

Stan realizes that he had been ignorant of the truth behind the war and the sacrifices made by Ryley, Gilac, and Heim. He apologizes sincerely to Wilbur and Heim and vows to complete the world that both the Demon King and his father died trying to create. He reaffirms his commitment to the job placement work and to the unfinished shared dream of true coexistence.