Daming on the Sea

In the fictional world, the earth is being ruled by a huge country called Ming Dynasty. The protagonist is the widow of the Ming Navy who was left in America. When he was a child, the male protagonist knew that he was Han Chinese and that his motherland was in the far west. The one closest to him is thousands of miles to the south. At this time, the Ming Dynasty is in turmoil. This global hegemon is decaying.