I understand what yal are saying, but if you really think about it it makes since. Despite of Koga, they want to prove the point the Sess.(abrveitation) is changing. He is becoming nicer. Is it Rin that caused this change? Who knows..but we see that Rin forgives Koga because afterwards she seems to be over what happened and back to being cheerful and bubbly. Sess.. used to kill just becuase, but we see that he has become a tad bit more linent and logical in reasoning who he kills. He realizes its pointless to kill people that are not a threat. I liked it. Besides, it gives other people in the show a chance to shine and prove that this show is not all about fighting and violence but forgivness and other stuff.