In another two or three years, two more prefectures will ask to join the Wood Dynasty—specific details will be determined as the situation develops. In the end, we will leave the Young Master only one prefecture. Actually, in my ideal scenario, it would be best to reduce him to a mere governorship.
Then, all of the Young Master's descendants will encounter premature deaths, no matter how many wives he marries, he will not be able to have any children.
Before that, we will prosecute the impostor king and decapitate all eligible successors in the Nanni royal clan, leaving only a few who obey us. The Young Master will have no choice but to adopt one of them.
When the Young Master dies—when we need him to die, we can arrange for him to leave this world—the successor will be our man. After a transition period of seven or eight years to a decade, we can have him submit a petition to abolish his royal title. My Wood Dynasty will then ensure his lifelong wealth and nobility.