Between January and February 1812, he made strenuous exertions and shut himself up at a temporary residence of Naofuru SHIBASAKI, a disciple in Fuchu, Suruga Province, and he at once finished writing several books about Kodai Kenkyu (Ancient Study), including "Koshiseibun", "Koshicho" (Clarification of Early History) and "Koshiden" (Commentary on Ancient History).
1811年（文化8年）大いに奮発する事があって師走には駿河国府中の門人柴崎直古の寓居に籠もり、『古史成文』『古史徴』『古史伝』など古代研究の本を一気に数多書き上げる。