Gaikaku is a genius mage with extraordinary magical and tactical abilities, but he deliberately keeps his talents hidden. He works as a secret assignment contractor under a gluttonous and incompetent regional lord named Borick, earning just enough money to fund his true passion: magical research. To avoid drawing attention, he surrounds himself with a small group of girls from various races who serve as his assistants and companions, and he lives a quiet, secluded life devoted to his studies.

Everything changes when Gaikaku is forced to take down an elite elf in a mission. The feat is so impressive that word of his abilities begins to spread. His cover is blown when the heroic female knight Tistoria, the kingdom's knight general, discovers his true competence. Instead of punishing him for hiding his skills, she recruits him and appoints him as the commander of a new knightly order.

Once his abilities are exposed, Gaikaku accepts his new position and begins to build and lead the "Circus Knights," a unique knight brigade that relies on tactical ingenuity, magical engineering, and unconventional warfare rather than brute strength. His harem of multiracial female subordinates expands as he takes in new members, including a beastwoman and a dark elf purchased as slaves, a dwarf engineer, and others. Each of them develops deep loyalty and affection for him as he demonstrates his brilliance and care.

The narrative follows Gaikaku as he leads his beautiful all-female knight order through a series of increasingly difficult missions. These include hunting down a band of deserters turned bandits, capturing a fortress in a single day to pass a knight entry trial, and later taking on a rescue mission to aid the elven forest homeland of one of his assistants. In every conflict, Gaikaku relies on his mastery of magic, clever tactics, and illegal or overlooked magical technology to achieve victory without casualties.

The setting is a fantasy kingdom where multiple races coexist, and the story emphasizes tactical combat, magical gadgetry, and the growing harem dynamic as Gaikaku's strength and kindness earn him the devotion of the women around him.