The Chousai (冢宰) serves under a ruler and is accountable for the six ministries of the court. Translated also as "Prime Minister" and "High Mandarin," the chousai is the kingdom's top administrator. During periods where no monarch sits upon the throne, the chousai wields considerable power as the effective ruler of the kingdom until the next monarch is chosen.
- Seikyou - The Chousai of Kei during the reign of Jokaku and early in Youko's reign; later arrested and removed from office on charges of corruption
- Koukan - Seikyou's successor, the former Governor of the Province of Baku in Kei
- Hakutaku - The Chousai of En, formerly the chief advisor to the Governor of Gen Province
- Eishuku - The Chousai of Sai during the reign of Shishou
- Shouyou - The Chousai of Hou after the fall of Chuutatsu, formerly the Taisai of Hou