Iwata Koichi and Kagawa Midori are second-year students at Tozaiyama High School. One day, while coming home from school, they discover a shooting star rising up in the sky. The next day, Midori sees a shining figure in school and everyone on the school grounds starts talking about a ghost. At that point, a mysterious transfer student called Yamazawa Norio suddenly arrives at the school and moves in to live next door to Koichi. Strange things begin to happen frequently around Koichi whenever Norio appears. The reason and objective of Norio’s arrival in this world is gradually revealed.
Tokine Amino works as a secretary for TEN2, an advertising agency. One day while cleaning the conference room, she is surrounded in light and finds she can't leave the room until she solves a puzzle. It seems a creature named Hacchin is a being from another dimension called Quizn. He is interested in the intellectual pleasure that happens when someone solves a puzzles or uncovers a mystery. And he has his sight set on Tokine Amino.
Akira is a normal high school boy, but he nevertheless impulsively licks some drool left by the mysterious transfer student Mikoto. The next day he falls asleep with an inexplicable fever. After five days Mikoto suddenly comes to visit, and makes him consume her drool. The fever instantly vanishes, and Mikoto explains that he's suffering from "love sickness." She can transmit emotions through her drool, and the two of them are now bound together.
"The After-Dinner Mysteries" is a daring mystery with unique characters, play on words and witty conversations. Reiko Hosho is the only daughter to the CEO of a major enterprise, "Hosho Group," known worldwide. Hiding her true identity behind her day time job as a rookie police officer, Reiko comes home to Kageyama, her butler whenever she is faced with a complex case. Being a perfectionist, Kageyama is flawless when it comes to serving meals full course from hors d'oeuvre to dessert. He sharply points out the lack of reasoning on Reiko's side by making cutting remarks, but keeping the comment a fine line away from being offensive.
The story is set in London and follows Katrielle as she solves mysteries with her talking dog Sherl.