A Kamakura-period court noble and effective founder of the Saionji family. He rose to the rank of Grand Minister (Daijo-daijin). During the Jokyu War (1221), he reportedly leaked Emperor Go-Toba's war plans to Kamakura. After the war, he wielded immense power as mediator between court and shogunate, marrying granddaughters into the imperial family. The Saionji house monopolized the role of Kanto Moshitsugi (liaison to the shogunate), becoming indispensable in court-military relations. He built the magnificent Saionji temple at Kitayama, which later became the site of Ashikaga Yoshimitsu's Kinkaku-ji (Golden Pavilion).

A pragmatic realist with exceptional political instincts. His decision to side with the shogunate during the Jokyu War demonstrated his ability to read the times. Though a courtier, he prioritized cooperation with the warrior government.

The Saionji family, as Kanto Moshitsugi, became the linchpin of court-shogunate relations and the most powerful court family throughout the Kamakura period. The Kitayama estate became the site of Kinkaku-ji, leaving a mark on Japanese cultural history.