Usoyomi to Gishoku no Oujo

The setting is a court romance set in the Ryugu Kingdom in the south. Oto, a girl whose family was destroyed by the King of Ryugu, invades the court to kill the princess, but fails. The opponent Oto tried to kill was self-proclaimed the princess' replacement, and he was a man. As Oto is depressed, Asu tries to escape from the castle.