A young man known as Utsu Dai Sensei, or simply Great Teacher, drifts through modern Japan as a clever but parasitic recluse, living off multiple partners and avoiding stable employment. When a sudden nuclear war erupts, he and his sharp‑elbowed acquaintance Coneshima flee into a shelter and are abruptly transported to a medieval fantasy world. There they discover the remnants of a lost civilization’s advanced technology, and Coneshima seizes the opportunity to rebuild it, founding the Coneshima Kingdom. Guided by utilitarian philosophy, he pursues the greatest happiness for the greatest number, restoring science and industry while ruthlessly maximizing profit and efficiency. Opposing him is a powerful church that condemns science and champions absolute equality. The charismatic militant Spartacus, a freedom fighter trained in the kingdom’s ranks, plots to purge the church altogether, dragging the reluctant Great Teacher into the conflict.

As Coneshima’s war mobilizes all subjects under a policy of total conscription, the kingdom descends into brutal, ideologically charged warfare. After the king’s excesses are curbed, a parliamentary system is introduced, and citizens gain the vote. Great Teacher, along with the earnest Roboro and other members of the real‑life let’s‑play group 〇〇の主役は我々だ!, now voices their own political philosophies, turning the kingdom into a turbulent laboratory of ideas. A failed expedition to destroy the monstrous Zakkum destabilizes the realm, sparking a clash between Roboro’s parliamentary faction and a shadowy royalist group pushing for a return to absolute monarchy. Exploiting the chaos, the warlord Gruppen leads the Zochi Empire in a full‑scale invasion. Coneshima Kingdom fights back with a mysterious holy ark, but Zakkum’s overwhelming power forces the king into agonising decisions.

Later, the story shifts to the Tonton Town arc. Great Teacher and his allies arrive at a border town where Margrave Tonton has saturated society with the principle of “fairness”. The town’s laws are so meticulously crafted that the protagonists exploit loopholes to pursue pleasure legally, slowly corrupting the community. Young Chiino, inspired by the warrior Zom’s example, undergoes a profound change, while the immigrant Zomzom Group reveals its true agenda. The tension culminates in the town’s assembly, where Great Teacher’s lobbying skills are put to the test. Throughout these arcs, the manga weaves philosophical questions about happiness, justice, freedom, and the meaning of being a protagonist in a world where every character lives by a different set of beliefs.