Harley Hartwell, known in Japan as Heiji Hattori, is a high school detective from Osaka and Jimmy Kudo's rival. His intelligence is at par with that of Jimmy, which often leads to intense rivalry between them. He later becomes friends with Conan Edogawa after discovering his true identity as Jimmy. Although he tries to hide it, he often gets concerned for Jimmy's safety when dealing with the Black Organization and warns him to be careful. He has a relationship with Kazuha Toyama, his childhood friend and love interest.

He should have a normal, youthful sounding voice, just a teenage detective