Shihai monjo (紙背文書)
Shihai monjo refers to the monjo (ancient document) written on washi (Japanese paper) before another monjo was then written on the other side of that same piece of paper. Because the monjo written later was considered the main one, the one written first was regarded as being written on the back side of the paper. Shihai monjo is also called ura monjo.
Since washi (Japanese paper) was valuable in ancient times, once paper was used, the back side of the paper, which was blank, was reused for other writing; this method for recycling Japanese paper was utilized along with sukigaeshi gami (paper made by redissolving used paper). In addition, writing a diary on the blank space of guchureki (annotated calendar) had been practiced since the Nara period and when more space was needed, extra lines were added on the back side of the calendar. Besides these, there are monjo composed of casual references written on the back side of used paper (which was relatively easy to procure), to be turned later into a fuller version with new parts or from which a fair copy could be made. There are many important shihai monjo in the history of the development of kana (syllabic Japanese scripts) related to manyo-gana (an ancient form of Japanese kana using Chinese characters to represent Japanese sounds) and kanashosoku (a letter written in kana).
Documents kept in the middle section of the Shosoin (the Treasure House) are called shosoin monjo. After koseki (Japanese family registry) and other official documents under the ritsuryo system (the historical law system based on the philosophies of Confucianism and Chinese Legalism in Japan) ended up at Todai-ji Temple as scrap paper, the back side of that paper was used for creating records. There are many types of shihai monjo including "Sokoshujitsu" (voucher issued by a bookbinder) and "Shosoin Manyo-gana Monjo" (two sets of monjo exclusively written in manyo-gana stored in the Shosoin Treasure House).
Shosoin Manyo-gana Monjo ('和可夜之奈比乃 [waga yashinahino]...')
Shosoin Manyo-gana Monjo ('布多止己呂乃 [futa tokorono]...')
Nichiren used the back side of Gyosei monjo (administrative written materials) which were used by the Chiba clan and given to Nichiren by Tsunenobu TOKI, a vassal of the Chiba clan, to write letters to his disciples and patrons of the temple. Those letters are kept in Nakayama Hokekyo-ji Temple and other places.
Diaries written by court nobles and Buddhist monks from the Heian to Edo period.
"Meigetsuki" (Chronicle of the Bright Moon) by FUJIWARA no Teika
"Kennaiki" (Diary of Tokifusa MADENOKOJI) by Tokifusa MADENOKOJI
"Daijo-in Jisha Zojiki" (Notes of Daijo-in on Various Matters of the Shrine-temple Multiplex) by Jinson
"Gien Jugo Nikki" (Diary of Gien, who was given the title Jugo [an honorary rank next to Emperor, Empress Dowager, and Empress]) by Gien