Teishinko-ki (貞信公記)

Teishinko-ki is the diary of Kanpaku Dajodaijin (imperial regent and grand minister) FUJIWARA no Tadahira.

The diary's title derives from Tadahira's shigo (posthumous name) 'Teishinko,' but the is also called "Teishinko Gyoki." It is a fundamental historical resource for understanding the political history of the first half of the 10th century and contains many descriptions relating to imperial court etiquette and government affairs.

The surviving parts pertain to the period from the year 907 when Tadahira was aged 28 to the year 948, with sections missing within this period.

The original detailed diary written by Tadahira no longer survives, and the extant "Teishinko-ki" is a transcription that was made by Tadahira's eldest son FUJIWARA no Saneyori. For this reason descriptions are shortened and there are few details of the procedures of imperial court ceremonies or government affairs as can be found in other diaries. Annotations written as 'private notes' have also been added by Saneyori. Another feature is that many of the dates with notes were excerpted from the calender when Saneyori transcribed the diary, so it is known the original work was written according to the guchureki (Japanese lunisolar calendar). FUJIWARA no Michinaga's diary, "Mido Kanpaku-ki," was also written according to the guchureki.

The Kujo Moto Koshakuke Bon manuscript (early Kamakura period; Important Cultural Property) is held by the Tenri Central Library and the Hisamatsu Bon manuscript is held by Kyoto University. Manuscripts are also held by locations including the Imperial Household Archives, Sonkeikaku-bunko Library and the Jingu Library. Writings that were lost from this diary can be seen in other works including "Saikyuki" (record of court practices and usage, written by MINAMOTO no Takaaki in Chinese style) and "Hokuzansho" (a representative book of ceremonies for the Heian period written by FUJIWARA no Kinto).

Printed copies of the diary are included within "Dainihon Kokiroku" and "Zokuzoku Gunsho Ruiju." A printed copy of the Kujo Moto Koshakuke Bon manuscript is published as the "Tenri Toshokan Zenpon Sosho" (Tenri Central Library unabridged book collection).