Against my better judgement, I've decided to include Koga as one of the heros, although his heroism only extends to protecting Kagome.  What can one say about Koga?  Besides being stupid, macho, and completely crazy, Koga's an okay guy.  As leader of the Wolf-Demon tribe, he's got about fifty followers, most notably Ginta and Hakaku (did i spell that right?), who are always chasing after him.  In Episode 36:  Kagome Kidnapped by Koga, the Wolf-Demon, Koga makes his premier as a villain, not a semi-hero, when he invades a village and allows his wolves to eat or kill everyone, including poor Rin!  Mainly Koga just randomly appears.  He's not like most other characters in the show that have some kind of definite pattern of appearance and disappearance.  Rather, he just shows up.  He and Inuyasha fight a lot.  Kagome subdues Inuyasha.  Koga runs away.  That's about it.