my opinion is that Narfi is a werewolf... listen to this quote, "No more sleep, no, no, no!" and another, "Oh Reyda, you are high in the clouds now, high, high, high! Just like the moon!". these two quotes are examples of a werewolf... they metion the moom and they cant sleep. now there is no specific evidence that he killed his sister or not... but go to were she was killed... somewhere nearby you willl find "2" iron arrows. now do you think it was Narfi or bandits? Have fun everyone!