Game concept · All Under Heaven
Restored Emperor
The game also links it as Restored Emperor's.
From the game's encyclopedia
A Restored Emperor is a Ten'nō who governs independently of a Ruling Regent.
To become a Restored Emperor, a Ten'nō may be installed by a Restore Ceremonial Monarch Faction, or use the Restore Direct Imperial Rule Decision after becoming Ruling Regent.
The game's text for patch 1.20.1.2. Words in blue are entries of the encyclopedia: hover one to read it, as in the game.
Restored Emperor is an entry of Crusader Kings III's in-game encyclopedia (All Under Heaven). The game explains it: "A Restored Emperor is a Ten'nō who governs independently of a Ruling Regent." It is part of Ruling Regent. The game also links it as Restored Emperor's. Patch 1.20.1.2, from game/common/game_concepts/tgp_game_concepts.txt and game/localization/english/game_concepts_l_english.yml.
Source: game/common/game_concepts/tgp_game_concepts.txt, game/localization/english/game_concepts_l_english.yml and the English localisation, Crusader Kings III 1.20.1.2.