Debut Episodes of Rival Characters in Detective Conan (Case Closed)?


I used to watch Detective Conan when I was younger and remember I got through
the first 100 or so episodes. The most prominent "rivals" of Conan from what I
remember was Kaitou Kid and Heiji Hattori. Who are some other characters that
come later in the series and which episodes do they first appear?




Kaitou Kid isn't really a rival character, he's somewhat of an antagonist.

Other than Heiji, there's only Sera Masumi who is a recurring character and a
detective.  
She first appears in episode 646.

