A prominent Tendai monk and historian of the early Kamakura period. Born into court aristocracy as a brother of the regent Kujo Kanezane, he served as Tendai Zasu (head of the Tendai school) four times. He authored the Gukansho, interpreting history from Emperor Jimmu to Emperor Juntoku through the concept of "dori" (reason/principle). This groundbreaking work is considered Japan's first philosophy of history. Written just before the Jokyu War, its sober view of warrior rule as a historical inevitability was remarkably unusual for a courtier. He was also an accomplished poet, with many works included in the Shin Kokin Wakashu.

An intellectual of deep learning and dispassionate historical perspective. Despite his aristocratic background, he possessed the intellectual honesty to analyze the rise of warrior power objectively.

The Gukansho is a landmark in Japanese historiography, highly valued as the first attempt to interpret history through consistent principles. It influenced later works including Kitabatake Chikafusa's Jinno Shotoki.