Konyaku 13-nenme desu ga, Imadani Aisareteimasen: Aisaretai Oujo to Aisanai you ni Hisshi na Jiki Koushaku

https://www.cmoa.jp/title/344551/vol/4/ It has been 13 years since the innocent princess Frederica was engaged to the future duke, Strauss, at the age of five. Their relationship remains as close as siblings. Frederica longs to change their relationship into that of a loving man and woman. She begins to try every means possible to win his love. Seeing her determination, Strauss finally breaks down his walls, and his doting love becomes unstoppable.