The Emperor and/or Empress of Yamatai hold nearly absolute power over the Yamatai Star Empire. Traditionally, the Imperial Sovereigns have been members of (or adopted into) the Ketsurui Clan.

The role of the Imperial Sovereign is defined in The Constitution of Yamatai Star Empire. They are the senior leader of the Empire and the personifies the will of the Empire. In general they are able to approve or veto laws and treaties, ultimate power to interpret laws, appoint and direct the commander of the Star Army, grant pardons, and issue Imperial Decrees.

The Imperial Sovereign may choose a successor with the approval of the Senate. If there are multiple successors when their time as the Imperial Sovereign ends, a general election is held to determine the next Emperor/Empress. If there are no successors, then the Imperial Premier becomes the Imperial Sovereign. As of YE 45: the Imperial Premier, Ketsurui-Shinjuku Hanako, would succeed to the throne.

1. Ketsurui Saito (YE 01-YE 02)
2. Nepleslian Emperor (YE 02-YE 08)
3. Kitsurugi Uesu (YE 08-YE 21)
4. Ketsurui Yuumi (YE 21-YE 23)
5. Ketsurui Yui (YE 25-YE 27)
6. Ketsurui Ayame (YE 27-YE 28)
7. Kitsurugi Uesu (YE 28-YE 30; Second term)
8. Ketsurui-Motoyoshi Katsuko (YE 30)
9. Ketsurui Himiko (YE 30-present)