Why not just assasinate the Emperor, Crown Prince and Second Prince? What a mess up Royal Family...
If they can't spill blood on their hands then let others do the work instead... Hire assassins & make/hire a informant guild for informations, digging every little bit by bit of scandals and disgusting information for evidence/proof to rival against the Emperor, Crown Prince, and Second Prince... Put the informations gathered in newspapers and hand it all to the people/townfolks, etc.











It would be easy if they just talk/communicate with each other so both parties won't have issues regarding their relationship, right?... ¯_(ツ)_/¯