Godfrey Daniels enters Manhattan Summoners High as the despised son of a war hero, mocked for failing to awaken naturally. His classmates, Dale, Siegfried, and Snow, torment him relentlessly, nearly killing him by throwing him off a balcony. Only Isolde Pendragon, the dragon-summoning prodigy, shows him any kindness. During the awakening ceremony, Godfrey steps onto the platform expecting failure, but instead finds himself in a vast soul space with a white staircase and a palace of many doors. The gauge reveals a King-tier potential of 12.1, a reading so shocking the headmaster hides it. Godfrey summons Mountain, a Knight-Captain of the Golden Order, a hybrid humanoid summon with the ability to copy enemy skills and enter a Black-Out State that boosts his tier. The world sees a low-tier humanoid summon, but Godfrey knows the truth, he is a monster in disguise.

After three weeks of training in green gate dungeons, Godfrey returns to Manhattan transformed. He has killed, faced life-and-death battles, and grown Mountain from Tier 3.0 to 3.4. During the school competition, he faces Maldred and then Siegfried, revealing Mountain's ability to copy innate skills and rise to Tier 5.0 in Black-Out State. The crowd is stunned as Godfrey defeats Siegfried, who secretly possessed a second summon. But the real shock comes when Cecil, the school news writer, overhears the headmaster and nurse discussing Godfrey's true King-tier potential. The revelation spreads like wildfire, though many refuse to believe it. Godfrey's victory earns him a place in the quarterfinals, but his enemies, Dale, Snow, and the Nexus Club, are already plotting his downfall.

The conflict escalates as Jon, Manhattan's King, targets Godfrey, banning him from the Nexus Club and sending his Hounds to attack him. Godfrey creates the Shadow Club with Isolde, Isaac, and Lucy, directly challenging the established hierarchy. During a football game between sophomores and juniors, Godfrey dominates, forcing Jon to intervene personally. Their confrontation ends with Godfrey losing an arm, but his third summon, Tempest the Chief Knight, emerges, revealing Godfrey as a Tri-Summoner. The battle shakes the school, and Yuan, Jon's right hand, is nearly killed. Godfrey is suspended for a month, but when he returns, he is hailed as a legend. The Shadow Club grows, and Godfrey's mother, Valentina, is rescued from the corrupt mayor and hospital director who had been poisoning her. The Pendragons intervene, and Godfrey's family is finally safe.

During a field trip to the Undead Desert, Godfrey and his friends face a new threat, Cain's Fanatics, who trap them in a green gate dungeon. The dungeon's boss, a powerful warlord, leads an army of undead and minotaurs. Godfrey's knights, Mountain, Ballista, and Tempest, fight alongside Percival Pendragon and other allies. In the climax, Godfrey faces an illusion created by Snow's butterfly summon, but Tempest's power breaks it. The battle reveals the depth of Godfrey's growth, his knights now at Tier 6.0 and beyond. After clearing the dungeon, Godfrey returns to find the school changed, the Nexus Club's tyranny broken, and himself hailed as a hero. But the final revelation comes when he discovers that Isolde's mother, Christie Pendragon, was the one who saved his family, and that the Pendragons have taken an interest in him. The semester ends with Godfrey standing at the threshold of a new power, the third door in his soul space beginning to open.