Demon Sword Maiden - Chapter 42Book 12: : The Queen’s Training

He died on the wedding of the girl he had a crush on, after a long and successful career. After convincing Yama to send him back to the world, he decides to fix the areas in which his life went wrong. Realizing the lack of love and romance in his past life, he sets out to conquer the hearts of various women.

- Description from Novelupdates

This is a world where a king is the most powerful.

The poor Commandery Princess is down and out. Her father died when she was young, and her mother passed away not long ago. Her grandfather, the only one she can rely on, is now at death’s door from his illness. Faced with the merciless uncle, the greedy aunts, as well as cousins competing to present the model of the worst relatives, the Commandery Princess could do nothing but feel depressed in heart.

She was a medical genius from the Noah Medical Academy as well as a drug producing specialist. After sleeping for three days, she had returned to the ancient era and become the loyal marquis palace’s ignorant and silly young miss.