For 10 points,  name this tradition, many of whose myths were created during the Silla and Goguryeo Dynasties.
One myth from this tradition describes a messenger with a red belt and purple robe who emerged from a chest, bearing  five grains and three girls, each of whom married a demigod. One hero from this tradition was once cornered at a river  while being pursued by enemy horsemen, but was able to cross on the backs of fish. This tradition holds that two heavenly  men and two heavenly women were the progenitors of mankind, having been birthed by Mago. In this tradition, a tiger  chased a pair of siblings who became the sun and moon. After passing a hundred-year trial in a dark cave, a (*) bear  transformed into a beautiful woman on the last day in this tradition, in which the gumiho is a fox who can seduce men in the guise  of a beautiful woman. Many myths in this tradition have different versions in the mainland and on Cheju Island. For 10 points,  name this tradition, many of whose myths were created during the Silla and Goguryeo Dynasties.
One myth from this tradition describes a messenger with a red belt and purple robe who emerged from a chest, bearing  five grains and three girls, each of whom married a demigod.
Korean mythology