As it was said that 'if the Imperial Palace (Ashikaga Shogunate house) ceased, Kira succeeded and if Kira ceased, Imawaga succeeded,' the Kira clan and Imawaga clan were special families that had the right of succession to the head family of Ashikaga and the Seii taishogun (great general who subdues the barbarians) if the head family of Ashikaga (Muromachi shogunate family and Kamakura kubo [shogunate] family) ceased.
「御所（足利将軍家）が絶えなば吉良が継ぎ、吉良が絶えなば今川が継ぐ」と言われていたように、足利宗家（室町将軍家系統と鎌倉公方家系統）が断絶した場合には吉良家とともに足利宗家と征夷大将軍職の継承権が発生する特別な家柄であった。