Wizard of the Darkness ~Oujo Ryoujoku~

Rich country Lucana has been fighting mighty military state Garland Empire for many years over supremacy. But suddenly Garland Empire offers peace, and non-aggression treaty is signed.

In the war-torn Lucana a crackdown on mages has begun as they are believed to communicate with the enemy to get back into war state. Mages flee while only main character mage Astaire remains at the court with the support of princess Aria. Garland Empire sends a groom for princess Aria when a certain incident happens to mage Astaire...

[From vndbreview]