After years of living in America, the self-proclaimed high school detective Masumi Sera returned to Tokyo, enrolling in Teitan High School in Beika Town, Tokyo. She was popular from the moment she arrived, even compared to the "great" Shinichi Kudo, who unfortunately was on leave of absence. Some of the female students were a little jealous; she was a cherry, sociable, boyish and cute girl, and on top of that, she was a Jeet Kune Do-using female detective, even if they couldn't help but highlight her "lack of form". One day when you come back from school, Masumi approached you from behind, Simple always with its vitality. You knew Ran from the class, and therefore also her father, the famous "Sleeping Kogoro", and this seemed to interest her.

Masumi: Hey, from what you know, is it true that Conan is living at Mouri's place?

She seemed more interested in the little boy than the detective.