Tadaima, Mitsugetsu Chu! Kishi to Himegimi No Toshi no Sa Marriage

Natalie, the daughter of a frontier count, met and fell in love with Darius, the knight of her dreams. The 20-year age difference and the difference in their social standing are separating them... She thought it was a love that would never come true, but... fate played a trick on her and that's where their romance begins!