Meitantei Kouko wa Yuuutsu

In the Showa era, Japan had a law awarding a detective diploma only to those who solved three challenging cases. Kouko, who wants to become a detective, is asked to uncover who is threatening to kill Inukami-kun, the son of a prominent family staying at Shunjukan, a Tokyo boarding house. To investigate, Kouko poses as a cook responsible for the lodgers. However, she struggles with both cooking and logical thinking, making her work difficult. The four other residents of Shunjukan are all eccentric, adding to the complications.