Veyron City—a mega-floating metropolis created from the discovery of new energy sources. Shuu, a young man who owns and operates a small business in the area, leads a meager life due to his reckless spending. Kisara, a girl who visits Shuu's office and home because she is constantly concerned about him. She works while attending high school in Veyron City, doing everything from clerical work to housework. Ayano, Shuu's ex-girlfriend and a senior colleague at the corporation he had previously worked for, is also worried about him. Thus begins the slapstick romantic comedy of three people in a slightly unusual relationship that takes place on an artificial island in the Pacific Ocean.

Alto Goldfilled, a diligent student at the Ortigia Academy of Magic, aspires to become a powerful sorcerer. But he is unable to become one as, despite his excellent grades and strong commitment to his studies, he fails his summoning class. With the threat of repeating a year hanging over his head, Alto tries following an old, worn-out grimoire in a desperate attempt to resolve his situation. To his surprise, he succeeds and summons a powerful demon named Vermeil. As a sign of gratitude for releasing her, Vermeil agrees to become Alto's familiar, sealing their relationship with a deep kiss. Little does Alto know what else he is capable of and what Vermeil's past hides.

After finishing their "debut," Kate, Emilico and three other pairs who started with them begin a new life as adults.

Life back on the cruise following the Island Special Examination is anything but smooth sailing. Almost immediately after their return, the first-year students of Tokyo Metropolitan Advanced Nurturing High School face yet another special exam, with both class and individual points on the line. In addition to the complicated ruleset, more issues arise in the form of Kakeru Ryuuen and Kei Karuizawa. Angered by the previous test's outcome, Ryuuen is dead set on outdoing every class in the new challenge using any means necessary. Meanwhile, Karuizawa, a crucial pillar of Class D, is close to crumbling under the pressure of her past. The stage is now set for Kiyotaka Ayanokouji to once again—using the full extent of his planning, foresight, and ruthless manipulation—steer Class D to victory as dangerously close enemy forces try to bring it down.