The Ariwara clan (在原氏)

The Ariwara clan originated from Emperor Heizei's Prince, Imperial Prince Abo and Imperial Prince Takaoka's children were demoted from nobility to subject, and they were the clan whose ancestors were from Imperial Family. (Please refer to the Imperial Family members who were demoted from nobility to subject.)
The common clan was Imperial Abo's clan, they were the descendants of the brothers of ARIWARA no Yukihira and ARIWARA no Narihira who were demoted to subjects and became successful. They spent days in obscurity during Emperor Montoku's era, however the Ariwara clan became successful during Emperor Seiwa's era. Once powerful clans established a daigaku besso (a dormitory facility built near the University for the court noble's children), the Ariwara clan also established Shogakuin and send their children to study there.

It was said Narimasa NAGANO and Narimori NAGANO, father and son, who were the Uesugi clan's aides in the age of civil war were Ariwara clan's descendants.
Later on, there was also a theory that the Ariwara clan was from the Hirate clan, which Masahide HIRATE, a chief retainer of the Oda clan of Owari Province, who was in the blood line of the Arao clan with the Ariwara surname. (Another theory was the Hirade clan was from the Sugawara clan, the Kamo clan or there is an oral tradition that the Hirate clan was from the Serada clan of the Nitta clan line.)

[Original Japanese]