Board Thread:Theories and Speculation/@comment-24824859-20141204001040/@comment-25319350-20141204005539

It's likely that Hamura mated with a mortal woman before he went to the moon to guard the Demonic Statue. Back on Earth, the woman had a child who had the Byakugan and passed it on to his/her own descendents who eventually became the Hyuga Clan.