Later, some powerful families in the government occupied the higher Naii ranks and retained their privilege by succeeding Oni (the automatic promotion system in which the people at the age of 21 whose parents were from Imperial to the fifth rank or grandparents upper than third rank, were conferred an Imperial title).
のちに中央でも有力な一部の家系が上位の内位を独占して蔭位の恩恵を受けることで世襲してその恩恵を維持することとなった。