Hattori Heiji is a high school detective from Osaka, titled Great Detective of the West. He came to Tokyo to test himself against Shinichi. Thanks to his detective skills, Heiji eventually figured out that Conan is the brains behind Mouri, and that Conan is in fact Shinichi. The two become good friends after that, working on cases together when the opportunity arises. Occasionally Heiji gets Conan into a tight spot by calling him Kudou in front of Ran, but thanks to his puns, everything always seems alright.

Heiji has a strong Kansai accent and he can't seem to speak standard Japanese because his accent is so strong. Heiji is the son of the Osaka district police commissioner (a position at the top of the hierarchy), but Heiji prefers to get by on his own merits. Heiji gets his slightly dark skin from his grandfather. His childhood friend, Toyama Kazuha, has a budding, but denied romance going with him. In Detective Conan's 7th movie, it's revealed that Kazuha is apparently Heiji's first love, but Kazuha didn't know about it.

(Source: Tanteikid.com)