Demodori (Moto) Oujo to Ichizu na Kishi

Eight years after entering a political marriage, the youngest princess Adel returns to her native country. What awaited her was a marriage proposal from her first love, her attending knight Lewis. She is surprised to find that the once young boy with a cute face has grown into a handsome and dignified young man. Adel can hardly accept the reality of her unexpected partner. The royal romantic comedy of an eccentric, slightly delusional former princess and a straight-laced knight who complicates her love life!

(Source: FK Comics, translated)