The following is written on the okuzuke (ordinarily the last page of a book where the author name, publisher's name, etc. are written): Originally, there were five letters, but one of them was stolen and another one was requested by Hidetsugu TOYOTOMI and was presented to him in 1592.
もとは5通あったが、1通は盗まれ、1通は豊臣秀次の所望により、天正20年（1592年）献上したことが巻末の奥付に記されている。