Seishinko-ki is the diary of FUJIWARA no Saneyori who acted as a Kanpaku (chief adviser to the emperor) in the mid Heian period. The name 'Seishinko' is Saneyori's Shigo (posthumous title), and ''Seishinko-ki'' is also referred to as Suishinki which is named after the left-hand radicals of the Chinese characters (清慎), and Ononomiyaki which is named after Saneyori's mansion. These names, however, came into use after the death of Saneyori, who himself referred to it as simply 'Shiki' (a private record) which was a term the nobility commonly used for their personal diaries at that time.
FUJIWARA no Saneyori is known for his deep study of Girei (rites), and the diary, is said to include many definitions about the rituals and customs of the imperial court, later it became the primary written material in a school called Ononomiya line, of which he was the founder.
According to an anecdote, there was an incident in which the whole collection of the original book of ''Seishinko-ki'' was cut into pieces because Saneyori's grandchild - FUJIWARA no Kinto – cut and pasted the original book of ''Seishinko-ki'' when he was making up 'Burui,' a descriptive content of ''Seishinko-ki'' broken into categories, and his cousin-FUJIWARA no Sanesuke was inflamed with rage. (''Shoyuki'' Sep 14, 1020/Aug 9, 1025/Jul 31, 1028 etc.)
It is said that Sanesuke was furious because Kinto spoiled the original book, which had belonged to him, a direct descendant of the Ononomiya family, by cutting and pasting it without any permission. Furthermore, a part of the 'Burui' that Kinto made was destroyed in a fire when it was kept in the house of FUJIWARA no Norimichi (according to ''Shoyuki'' May 9, 1015) who was Kinto's adopted son-in-law, and later the 6 volumes that were assumed to be remains of the 'Burui,' were handed over to FUJIWARA no Munetada (the author of "Chuyuki") from FUJIWARA no Akinaka in exchange for lumber, and later were lent to Cloistered Emperor Shirakawa. However, Munetada didn't recognize the book, simply titled 'Shiki,' as ''Seishinko-ki,'' and later there was a conflict between Akinaka who claimed he gave the book to Munetada, and Munetada who claimed he didn't receive it. As the 6 volumes were also later scattered and ultimately lost, no copies have been found today.