Once the Emperor Saga took after the Emperor Heijo in 809, Nakanari and Kusuko siblings, who feared the loss of political power, moved to Heijokyo with the retired emperor and schemed to carry out the choso (a second accession to the imperial throne) of the retired emperor and caused a conflict between the imperial courts located at different locations.
809年（大同4年）平城天皇が嵯峨天皇に譲位すると、権勢の失墜を恐れれた仲成・薬子兄妹は上皇とともに平城京に移り上皇の重祚を画策して二所朝廷の対立を招く。