Comments of chapter undefined of Starting Today I'll Work As A City Lord

i have been wondering for some time, do they not have a king or an emperor? are they not under a country? for all I know, i dont think selling a nobles title is as easy as merely signing a contract between 2 people. how would thr imperial palace document the changes of the title holder? aside from that, nobles have limitations im their lands, for example, barons would only be allowed to raise up to 10000 military units or what ever. a nobles land should also just be limited to the scope of the city, it should encompass a lot more than the city, meaning, depending which land his noble title holds, they are sometimes given lands encompassing quite a large area.