Honchotsugan (本朝通鑑)

Honchotsugan is a history book in classical Chinese and in chronological order edited by the Edo Shogunate. Completed in 1670. Total 310 volumes.

Honchotsugan was edited as a historiography project by the Edo Shogunate, with father and son of the Hayashi family, Razan HAYASHI and Gaho (Shunsai) HAYASHI, as main editors. It was a 310-volume book of complete Japanese history: first 3 volumes (the age of the gods), the main 40 volumes (main volumes were based on "Honchohennenroku" describing the era from Emperor Jimmu to Emperor Uda), and the sequel of 230 volume (the era from Emperor Daigo to Emperor Goyosei).

The book covered the period from the age of the gods to the era of Emperor Goyosei (1586-1611). It is said that the principle of Honchotsugan was to depict the facts of history without ethical judgments.

A historiography project under the rule of the third shogun Iemitsu TOKUGAWA edited by Razan Hayashi was "Honcho hennenroku" that was published in 1640 but lost in the Great Fire of Meireki in 1657. In October 1662, as the Shogun Ietsuna TOKUGAWA's will, Gaho Hayashi was ordered to complete the chronological record of history, and in August 1663 the Shogunate approved the project by hosho (a document for informing lower-rank people of the decision of upper people such as an emperor or shogun) with signatures of roju (senior councillors of the Tokugawa shogunate), and the edit work started at the residence of Hayashi in Shinobugaoka. There was no official document of history after the Engi era and it was very difficult to collect historical documents; in the following 1664, Gaho requested a roju Tadakiyo SAKAI to provide necessary assistance such as collecting ancient records. In July, Naotsune NAGAI was appointed to bugyo (commissioner) who ordered territorial lords, the Imperial court, temples and shrines to submit the records that they owned. In August, the Kokushikan (Kobun-in) was built in the Hayashi's premise as the editorial office funded by the shogunate to proceed the full-scale project.

In 1662 while the editing was in process, the regime change occurred in China from the Ming Dynasty to the Qing dynasty, and it gave an impact on the historiography project by the Edo Shogunate in Japan. The title of the book was "Honchohennenroku" at first, but it was changed to "Honchotsugan" modeled on "shijitsugan," a history book of Sung dynasty in China. The editing process took 7 years to complete in 1670 and in June of that year, a draft was submitted to the Shogunate. The clean copied books were offered to Momijiyama Library and Nikko Tosho-gu Shrine.

It is said that Mitsukuni TOKUGAWA of the Mito clan was very angry when he found a sentence that "(Japanese are) descendants of Count Tai of Wu," thus motivated to start his own historiography project, resulting in a biographical history book "Dainihonshi" (Great history of Japan) that actively commented on people in the history, on the contrary to "Honchotsugan" in chronological order.