In the last years, he concentrated on writing as a scholar; the history book named "Nan-Tahiheiki" was meant to criticize the "Taiheiki" (The Record of the Great Peace), so he wrote about his position during the Oei War and great achievements made by the Imagawa clan which were not written in the "Taiheiki."
晩年には学者として著作に専念し、『難太平記』は古典『太平記』を難ずる意味の歴史書で、応永の乱における自らの立場や、太平記に記されない一族の功績を記している。