In Shintō (Japanese mythology), at the begin when earth and sky seperated 5 kami (gods) appeared in a mental state, not physically visible.
After them (the ,special 'holy' gods') the 7 generations showed up.
Under them is the ancient God pairing, the siblings Izanami-no-Kami and Izanagi-no-Kami.
Since Shintoism is a religion only in Japan, it tells only from the creation of the nation.
The older gods gave Izanami-sama and Izanagi-sama the task to form the land with a jewel spear.
Both of them swirled the earth and the fluent earth up and as they put the spear out the water which fell down created the isles and nation of Japan.
Onógóró (The ,selfsolified island') was created.
After it followed the act of love and first Ebisu-sama (In the Kojiki ,Hiru-go') then ,Aha' (an Island) was born.
Izanami-sama and Izanagi-sama decided that those children werent good and abandoned them.
Fast forward, as all the islands had a ,worthy' personification, Japan was officially created. Back then it was called ,Oho-yashima-kuni' (Great Eight Isles Land) because Izanami-sama and Izanagi-sama went away after the first 8 islands were born. But as they came back more islands were added.
This marked the birth of Japan.
Kiku and Kuro are the children of Izanagi-no-Kami and Izanami-no-Kami.
Izanami-no-kami will be later reign Yomi (the underworld) and raise Kuro until China finds them, when Buddhism from China influences the Japanese Shintoism.
Izanagi-no-kami will be still in 'heaven' and raise Kiku until China find them at the same time.
I am sorry for the long explanation.