The retired Emperor Go-Saga, who started a cloister government, left a will stating that among the imperial princes, the younger brother Emperor Kameyama's descendant should succeed to the Imperial Throne instead of Emperor Go-Fukakusa's descendant, thus causing a mutual conflict; it was therefore decided by the Kamakura shougunate to share the Imperial Throne between ancestors from both sides on the basis of a ten-year rotation (Ryoto Teiritsu) and to continue running the cloister government.
院政を敷いた後嵯峨上皇が、自分の皇子のうち後深草天皇の子孫ではなく弟の亀山天皇の子孫が皇位を継承するよう遺言して崩御したために、後深草と亀山の間で対立が起こり、鎌倉幕府により、両者の子孫の間でほぼ十年をめどに交互に皇位を継承（両統迭立）し、院政を行うよう裁定された。