Meitantei Kouko wa Yuutsu

During the Showa era, there was a law in Japan that granted a detective diploma only to those who solved three difficult cases. Kouko, an aspiring detective, receives a request to find out who's threatening to murder Inukami-kun, the son of a prestigious family, who is staying at Shunjukan, a boarding house in Tokyo.

Kouko infiltrates Shu...