1 website of Institute of Historical Materials Compilation, University of Tokyo. Provide a series of materials such as Historical Materials of Great Japan, Ancient Records of Great Japan and Ancient Books of Great Japan for retrieval and reading. In addition, there are word collapse retrieval systems and other materials, such as "The Legacy of Peace" and "The Legacy of Kamakura".
National Library of Congress website. Provide some books that have passed the copyright period for free reading. You can see all the historical materials compiled before the war, such as the complete compilation of "Group Books and Classes", which is a part of the old national history series.
3. Search and reading services of ancient history gardens provided by Japanese research websites. Although the electronization of "Ancient Event Garden" is still in progress, many parts have been provided for retrieval. This set of books is similar to China's "political book", that is, the history of laws and regulations. If you are interested in related aspects, you can search and try.
4. A long-standing stumbling block. This is a website made by Taiwan Province people, which contains some major ancient Japanese classics, such as History of Six Kingdoms and Yan Xiti. It overlaps with the above-mentioned "national history series".
Almost all of the above are online basic information websites that can be used at present. I don't know which section of Japanese history you are interested in, but if you can elaborate, I can give you more detailed opinions. Because Baidu knows the answer specification, there is no URL link above, but it is still relatively easy to find, as long as you search in Baidu, you can also find it. If you have any questions, please keep asking questions.