@Khulmach Actually there aren't signs of either one, first chapter says Ran dies from him falling on her off a tree, which sounds accidental, and since he says here that killing her wasn't the preferred method he might not even have hated og Ran (I can't see him not disliking og Ran, though. Even if she was an ignorant child following her mother abusing him, that's just not going to cause an affectionate relationship).
As for leaving her in the caves, his father hit him, probably for the same logic you just said. Be fair though, he was also a kid at the same time, and Ran was the one who asked him to sneak away first. The kid probably snuck back without thinking too hard that a younger child who didn't know the caves would get lost there.