Entering the middle era of the Heian period, high-class nobles, dominant temples and shrines (or powerful groups in other words) took hold of the right to collect taxes in a province, acquiring the right to freely appoint kokushi there.
平安中期頃になると、高級貴族や有力寺社（権門勢家）が、ある国の租税収取権を掌握し、国司を自由に任命する権利を得るようになった。