The origin of Koujyouji is that after Ankokuji built by Takauji Ashikaga was burned down in Taiei 3(1344), Shigenari Ootaka re-built a temple and its name came from his name. Thus, the letter of Shigenari should be the most important treasure in the temple.
Shigenari Ootaka was also called Jiro, and ranked Iyonokami. He followed Takauji Ashikaga and was famous for that he used a 1.7m long sword.
The founder of the Ankokuji was Dainen priest. Takauji Ashikaga and Shigenari Ootaka embraced him. Thus, Shigenari was asked to re-build the temple by him.
This letter says that:
Dainen priest sent a letter to Shigenari to build the temple and Shigenari investigated the effect of the lie of the land and found out that there is no problem at all. Then, Shigenari applied to the local administrator and prepared to build the temple.
This letter shows the good relationship between them.
Explanation 
Koujyouji
