I'm not sure where and how any evidence they gather will help with dealing with the princess and Robin. The royal castle is all out of whack. They can present all the evidence in the world, but if the king says "No", it's all meaningless. The king already decided the princess can marry the con man Robin, breaking the former years long agreement with a ducal house, and that it's okay to label the princess's former fiancé a criminal and send him to the frontier. That's the reality. Somehow the king would need to walk over the queen and change his mind. That's the only thing that matters and mere evidence won't do it. Plus he needs to do it formally before he gets assassinated. Otherwise heads would need to roll for anything to change.
But then again, this is shoujo manga, so all bets are off.
Thanks for your patience while we worked on chapters 24 & 25! Next upload is the extras for volume 5, then we will proceed with working on volume 6.
I hope you had time for pizza amidst all the translation work!