Sword of Japan

Needs All Under Heaven, and heed the wiki's warning: do NOT start in 1178 - Japan is already Sōryō by then and this becomes miserable. Start 867 as Korehito (or 1066 as Chikahito). The 867 route is elegant: scheme and influence your way to the front of the succession line (the sitting Kampaku is old and obliging about dying), get elected regent, then ABDICATE - passing the ceremonial throne to your heir while you keep actual control, as the Japanese court historically did. Keep your heir first in line, wait for the Royal Prerogative innovation, and once you're playing the heir holding BOTH the Empire and the Chrysanthemum Throne (do not abdicate this time), pass crown authority 3 and take Restore Direct Imperial Rule. The 1066 route swaps the patience for a Depose scheme on the Kampaku.