Aha

Basically, that man with the blue eyes is Grace father. Her mom was a spy seductress to extract info from military ppl. The bombing on the chapel which killed the former king was because spy mom was the secretary of the royal guard, which is Grace dad. She leaked the info to the rebel, meaning the dad was involved with the bombing because of his stupidity. Leon used this as a blackmail to stop the investigation that he is hiding a rebel since the dad can be punish from being involved in the former kings death, even if he was not aware.