Game concept · All Under Heaven
East Asian Mansion
The game also links it as East Asian Mansions, Mansion, Mansions, Family Mansion, Family Mansions.
From the game's encyclopedia
A Mansion is a type of Domicile held by the House Head of notable Noble Families within Ritsuryō and Sōryō Realms. They represent private landholdings untied to any particular Landed Title.
East Asian Mansion may be constructed here to expand the family's wealth and Influence, and the Mansion will be inherited by future generations.
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.
East Asian Mansion is an entry of Crusader Kings III's in-game encyclopedia (All Under Heaven). The game explains it: "A Mansion is a type of Domicile held by the House Head of notable Noble Families within Ritsuryō and Sōryō Realms." It is part of Domicile. The game also links it as East Asian Mansions, Mansion, Mansions, Family Mansion and 1 more. 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.