The East-Asian brother and sister\'s marriage myth is just the question about the prohibition. However the most noteworthy thing in a brother and sister\'s marriage myth is not the prohibition itself, but the prohibition and the violation of legislation. The prohibiton and the lawful violation of prohibition are just subjects of a brother and sister\'s marriage myth. The incest prohibition in a brother and sister\'s marriage myth is not acting by an absolute legislation. When they violated \'Don\'t eat\' or \'Don\'t look back\', they would be punished by God but the consanguineous marriage of siblings was a permitted violation as the point of getting God\' permission through the test. And the result of the violation was not the punishment but the blessing being the founder of mankind. As we know through the flood bursted from the result of sin in the flood myth, the morals named the prohibition is the God\'s judgement and the organization of judgement. As being the God\'s judgement and decided by one transcendental value measure, it can not but be the system of \'good or evil\'. But there is the desire of getting over this judgement system, it is shown by the brother and sister\'s marriage myth. By this desire, the ethics overturning the system of \'good or evil\' is composed. The mythical discourse has as its theme the passage from the indifference to incest to its prohibition. The brother and sister\'s marriage myth, including simultaneously the narratives without the complex of prohibition and the narratives with the prohibition as the strong system of judgement is the mythical discourse hanging around the doorsill of just this passage.