Tengai Kodoku no Moto Koushaku Reijou, Youjo o Hirou: Saikyou ni Kawaii Musume to Shiawase ni Narimasu!

On the day of her wedding, Duke’s daughter Lina Elford finds her life thrown onto a path of hardship when war suddenly breaks out. The Crown Prince, Seiran, whom she was supposed to marry, was killed in battle. Without even a moment to grieve, her own family was framed for a crime and fell into ruin. Having lost her parents as well, Lina was banished alone to the frontier, where she prepared herself for death. But in that moment, Lina found a young girl who appeared to be a war orphan. To Lina, who was in the depths of despair, the little girl’s smile was her salvation and her hope. Lina named the girl "Aria" and resolved to become her mother—! Five years later, Aria and Lina were living peacefully in a frontier village. Immediately after taking Aria in, Lina was helped by the villagers and was able to make a living as an apothecary. It was all thanks to the knowledge of medicine and toxins she had acquired during her Crown Princess education. Though their life was by no means lavish, it was a happy one. Aria grew up healthy and strong, and the bond between mother and child deepened. It didn't take long for Lina to start doting on the pure, kind... and far-too-cute Aria. She believed this life would continue forever. However—. "...Lina?" The situation changes completely. Seiran, who was thought to have died in the war, appears before the two of them...!? The story of love and bonds spun by three people toyed with by fate begins now! *Source: Manga Up!, translated*