Generally speaking, Kou and Tyu are the concept of Confucianism. And, as we know, They were introduced into ancient Japan from China before an early time.
From the Tokugawa Era, there has always been an argument between Kou and Tyu. While, in China, Kou was taken much more seriously than Tyu. More important is that, Kou was also asserted in Buddhism. So, the concept of Kou was changing between Confucianism and Buddhism.
When the Confucianism books were broughted into Japan, from Nara Era to the middle of Heian Era, Kou was mainly accepted by the aristocracy class with it's contribution to the building of the law country. It is not sure that, whether Kou and Tyu were also widely accepted by the other classes or not. In Heike monogatari, there is also some description about Kou and Tyu. I will try to make a study of Heike monogatari to think about the meaning of Kou and Tyu, and how they were be accepted by the Samurai.