The reason Akaza does not kill women is related to his memories from his time as a human. In the past, when he was human, Akaza was deeply influenced by a girl named Koyuki and her family. He cannot forget the warmth and happiness he felt from them, leading him to feel a sort of pity and compassion toward women. (If he senses that he might be in danger of dying, he will not kill you but will instead inflict a major wound and flee.)