Deep in the forest, far from any human contact, there lives a child named Ryouma Takebayashi. He engages in the rather strange hobby of keeping various types of slimes as pets. Furthermore, despite his young age, he has a sturdy physique and good compatibility for magic. All of this is because, having endured much hardship in his previous life, three gods grace Ryouma with a second chance to pursue one goal: savor the wonders of life. After three years of comfortable solitude pass by, Ryouma meets people that will change his current life forever. When he encounters and helps some soldiers tend to their wounded comrade, the group convinces him to accompany them to visit the nearby town's ducal family. Ryouma agrees and soon embarks on a journey to explore the vast world beyond his home.

In Tokyo, there exists a peaceful cohabitation between supernatural creatures—elves, dwarves, vampires, and more—and humans. However, contrary to history, powerful dragons once ruled over this world of creatures and humans but have since disappeared. Consequently, a diabolical group under the alias Nine, who seek the miracles of the once godlike dragons, stirs up trouble in the streets of Tokyo, commiting mass murder and causing destruction. To combat the dangerous group of Nine, the police organize the Special 7—a group of highly skilled professionals whose abilities exceed those of ordinary humans. Caught up in a bank robbery turned hostage crisis, Seiji Nanatsuki, having recently become a detective, has a chance encounter with Shiori Ichinose, a member of Special 7. Assisting with the resolution of the robbery, Seiji is recognized for his clear sense of justice and refreshing character, suddenly earning him a spot on the elite unit. As he takes on new missions, Seiji finds that being a detective as part of Special 7 isn't the police work he expected, where working alongside a team of different species with special abilities and vibrant personalities brings unpredictability to his daily life and police work. While the everyday crime in Tokyo continues, Seiji and the Special 7 will fight not only to resolve special cases, but also obstruct the ill-intentioned plans of the merciless group of Nine.

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.

Having died in a car accident, Tsubasa Kurata—an otaku from modern Japan—is reborn in the Fremmevilla Kingdom, a medieval world where powerful mechs called Silhouette Knights are used to fight horrific demonic beasts. Born into a noble family under the name of Ernesti Echevarria and bestowed with prodigious magical abilities, he enrolls into Royal Laihaila Academy. This school of magic trains young men and women on how to pilot the Silhouette Knights, prepping them to protect the kingdom from threats, both demonic and human. Ernesti teams up with the twins named Adeltrud and Archid Olter with the goal to create his own Silhouette Knight one day, a feat unheard of for several centuries.