Long Xinmi is a simple and lively 17-year-old high school sophomore girl, but she has an identity that is destined to make her extraordinary. She is the daughter of the country's number one detective, but her life is very poor and she is not as wealthy as she imagined. In order to allow her to live a good life, her father decided to accept a foreign commission and go to Canada to investigate an internationally sensational criminal case. At the same time, he entrusted his daughter Long Xinmi to his newly adopted brother Narinosuke to take care of her temporarily.