Millennium Research Institute, a counseling office where bizarre requests come in. The head of the research institute, Ichirou Umoregi, also known as Akuma-kun, a genius boy who only appears once in 10,000 years. However, he doesn't know his real family. So Akuma-kun, along with his partner Mephisto III, pursue the mystery of his origin while challenging mysterious cases in this mysterious detective buddy story. (Source: Fandom)

Amane Todoroki is a young girl who is straightforward but also unthinking. She will try her very best in everything and say, I don't know how to answer you if you ask me whether this can be done. I just believe it can. If not, then nothing will get started! She easily gets stuck in her thinking, but she can also get easily moved at something small and start crying. (Source: MAL News)

Ten years have passed since Nagomu Irino left his home to pursue his dream that ultimately failed. He finally decides to return after hearing that his father—owner of the Kyoto sweets store Ryokushou—has been hospitalized. Worrying that no one would inherit the shop if his father passes away, Nagomu prepares himself to embrace his family's legacy and the art of making sweets⁠. Unsurprisingly, Nagomu discovers that his father has already chosen a different successor—a 10-year-old girl named Itsuka Yukihira, who was abandoned at Ryokushou by her father for reasons unknown. While she has since become a part of the family and is now the shop's poster girl, Itsuka still longs to see her father and follows all possible clues that may lead her to him. Sympathizing with Itsuka's situation, Nagomu's mother asks Nagomu to act as Itsuka's father, hoping that Itsuka will open up to him and relieve her pain, even if just a little. Starting on bad terms, Itsuka and Nagomu gradually learn more about each other, realizing that they are more similar than they had thought. Connected by their mutual love for both Ryokushou and its confections, their relationship as child and father figure begins to make lives around them a little bit sweeter.

Every 60 years, the heavens conduct a sacred ritual called ETM12. This custom involves selecting worthy Eto-musume—celestial beings representing different animals—to become one of the members of the Chinese zodiac, or Eto-shin. However, since the first ETM12 two thousand years ago, the original batch of Eto-shin reigns with no one being able to replace them. Nyaa-tan is a cat Eto-musume who aspires to become a member of the zodiac in the ongoing ETM12. Fulfilling her ambition requires her to secure 12 seals, one for each Eto-shin. To that end, she must win various types of battles using Sol/Lull—divine energy created by people's positive emotions. This task is not easy however, as her powers as an Eto-musume are far below the abilities of a single Eto-shin. As such, she needs a constant source of energy. But in a chance encounter, Nyaa-tan meets Takeru Amato, a man who has just transferred to the apartment where she is secretly staying. To Nyaa-tan's delight, Takeru discovers that he gives out high quality Sol/Lull—something that sets him apart from most people. With this, the story of Takeru and Nyaa-tan begins. As Takeru supports Nyaa-tan in her dreams, he meets the Eto-shin and begins to uncover a mysterious past.