They’re also known as “Izanagi-no-Mikoto” and “Izanami-no-Mikoto.” The use of the term “pair” here is a little flexible. Yes, they were a spousal couple, but also a sibling couple. In ancient mythology, incest doesn’t tend to be an issue, and there will be more of it. Let’s move on and not let that bother us–after all, kami aren’t human.
Unlike other many other myths about how the world was created, the Kojiki (and its counterpart, the Nihonshoki) only focus on Japan. The rest of the world is impure and full of barbarians, and frankly not worth considering (or so the exclusion would imply). Ancient Japan was not simply known as “The Land of the Rising Sun,” but as “The Land of the Gods”.
It was a rather complicated process, and at some points so graphic that in one of the first English translations, parts of the dialogue were translated into Latin instead!