Because he's incredibly jealous. He knows that he doesn't exactley confess his love for Kagome, so he knows she might leave him if he doesn't shape up. Also he's a little bit of an idiot.
My favorite characters are Mirroku, Inuyasha, and Sesshoumaru. I think Mirroku is so adorable. Him and Sango would be so cute together. The same with Inuyasha and Kagome. Sesshoumaru just kicks major ass and is the hottest!!!!
Inuyasha and Koga r my favorite characters! They have such a rivalry but the both rock. Plus they both care bout Kagome....no matter how much Inuyasha denise it.