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 Heiji Hattori Subaru Okiya/Shuichi Akai Rei Furuya/Bourbon Makoto Kyougaku Masumi Sera Eisuke Hondou Haibara Ai/Shiho Miyano Kazuha Toyama(Hattori Heiji's Love Interest) Black Organization(First,Second and Third in command-Third one is Gin and you should check the members) Maybe also check Ran's Mom and Kudo's Mom's rivalry,Kudo's father and Kid's father's rivalry
From Magic Kaitou- Aoko Nakamori(Kaitou Kid's Love Interest) Ginzo Nakamori Akako Koizumi Saguru Hakuba
From Yaiba- Yaiba Kurogane Soshi Okita
Also a crossover with Lupin the third