Meitantei Kouko wa Yuuutsu

The manga is set during the height of the Showa era, and centers on a little girl named Kouko who is in training to become a detective. She is hired by a notable family to find out who sent a death threat to the family's son Inugami, who currently resides in a dormitory in Tokyo. To this end, she moves in to the dormitory to begin her investigation, but she is bad at cooking and even worse at figuring out where to start with the case. (Source: ANN)