The Ozuki clan (小槻氏)
The Ozuki (Otsuki) was a Kuge (court nobles) clan which could trace its history back to ancient times.
Up to the Kamakura period, the clan went under their original surname Ozuki, but thereafter it was divided into the Mibu, Omiya, Mushika, and Murata families.
Summary
The Ozuki clan is believed to have originated with OCHIWAKE no Mikoto, an Imperial Prince of the eleventh Emperor Suinin.
The descendants of OCHIWAKE no Mikoto had used the name of OTSUKI no Yama no kimi until 875 when Imao (the founder of the Ozuki clan) was given the surname of Abo ason (second highest of the eight hereditary titles). Imao's son Masahira changed the name to Ozuki no Sukune after their home town Ozuki, Kurita-gun, Omi Province (present-day Shiga Prefecture) and thereafter the clan also went by the name of the Ne family (using the last character in Sukune).
(The Otsuki Taisha Shrine and the Otsuki-jinja Shrine still stand in Kurita-gun region today.)
Thereafter, generations of the Ozuki clan served as government officials (esp. ones of low to medium rank) and finally reached to the status of top Jige-ke (non-noble retainers who are not allowed into the Emperor's living quarters in the imperial palace). In the early Kamakura period, the clan split into the Mibu family, the descendants of OZUKI no Takamoto, and the Omiya family, the descendants of OZUKI no Hirofusa. The two families initially vied with each other for position, but the Omiya family ceased to exist when Koreharu OMIYA died in 1551 while the Mibu family kept positions of government official until the Meiji Restoration.
The other branch families include the Mushika family separated from the Omiya family in the Muromachi period and the Murata family from the Mibu family in the Edo period.
After the Meiji Restoration, the title of baron the was bestowed on the Mibu family.
Official duties
After appointed as Sashoshi (assistant recorder of the left) and Sanhakase (official in charge of teaching mathematics and looking after mathematicians), Imao was allowed to move to Heian-kyo (the ancient capital of Japan at present-day Kyoto) in 853 and became a government official both in name and reality. Thereafter, members of the Ozuki clan inherited the positions of Sanhakase and Shi (official in charge of recording and managing the official documents). After OZUKI no Tomochika was appointed to the position of Sadaishi (Taifu no shi (senior recorder of Junior Fifth Rank, Lower Grade)) in 996, many other members of the Ozuki clan were appointed to the position. Since the generation of OZUKI no Takanobu in the eleventh century, the Ozuki clan gained hereditary control over the position and solidified their status as a Kanmu family with authority over benkan (officials of the dajokan) and official works of the government.
In addition, the Ozuki clan managed Tonomoryo (Imperial Palace Keeper's Bureau) and the copper mines. Since the Ozuki clan was in charge of storing documents of the Imperial court, 'Mibuke Monjo' (documents of the Mibu family) are still in existence today.