In the town of Nagarekawa, Nanako Usami, an ordinary high school girl, is approached by her uncle to become a local idol or Locodol, partnering with upperclassman Yukari Kohinata to form the idol unit, Nagarekawa Girls. As the girls use their talent to promote Nagarekawa and their businesses, they are joined by Yui Mikoze, who acts as the local mascot, and Mirai Nazukari, who serves as Yui's substitute. (Source: Wikipedia)

Three hundred years ago, the newly reincarnated Azusa Aizawa had resolved to live a slow life forever. At that point, she would have never even thought of reaching level 99 through only killing slimes, let alone becoming the strongest being in the continent. Nevertheless, it is due to her strength and kindness that many girls from different backgrounds—including the dragon Laika, the elf Halkara, the demon queen Pecora, and even the anthropomorphized slime girls Falfa and Shalsha—are all drawn to her. With her ever-growing circle of companions, Azusa's laid-back adventures are far from over—and with even more girls appearing on her doorstep, her already enjoyable life is slated to become even livelier!

Miu Takigawa views the world from behind the safety of her bangs, content with peacefully passing unnoticed through life. Reserved and timid, Miu struggles to converse with or even smile at customers when at her part time job, but she works tirelessly to support her mother and precious little sister, Haru. It is a shock when a letter arrives from the entertainment company GIP, announcing that she has been chosen as a candidate for their new project. Miu decides to accept the invitation and heads to the meeting spot where the eccentric ensemble of other candidates filter in, all summoned by their own letters. Not long after, the girls are escorted by a manager to a luxurious secret facility, where it is explained that they must follow the mysterious directions of The Wall, whose orders are absolute. The 24th of December, 2016, will see the birth of idols like no other; on that day, the group 22/7 will debut, whether or not Miu and the other members are ready to take the stage.

Toys are powers bestowed upon those chosen to wield them, each having qualities that are unique to their users. Some of these individuals are born pure, using their powers to become detectives. Others bloom laced with poison and choose to become phantom thieves. These two opposing factions caused the formation of various detective academies around the globe—training detectives to fight and catch the phantom thieves. Sherlock Shellingford, Nero Yuzurizaki, Hercule Burton, and Cordelia Glauca form Milky Holmes, a group recognized as the cream of the crop in the Yokohama-based Holmes Detective Academy. However, in a skirmish against the phantom thief Arsene, their Toys suddenly disappear, deeming them unfit to continue as detectives. Stripped of their prestigious life and thrown into a rundown attic, they face expulsion if they fail to regain their powers within the next three months. Tantei Opera Milky Holmes tells the story of a once-legendary group in their journey to recover their Toys, as well as attempting to continue their line of work without the powers that once defined their career.