The koryu dynasty’s leaders believed that their politics should be guided by the principles of

shintoism.
buddhism.
confucianism.
taoism.

I believe the answer is: Confucianism.

The Koryu dynasty believe that the best of life that should be implemented by both citizens and the government officials would be extremely simple and driven by personal advancement rather than materialistic things. These views aligned with the teaching of confucianism that originated from China.

dirty, contaminated water

contaminated food,

chlostrophobic living spaces,

mice infestation,

etc,