Manhwa The main character is obsessed with my health

Grand Duke Valerian Slun Halbern. He is known as a cold, ruthless, and unwavering ruler of his lands. His name inspires respect and fear even among the highest nobility. However, all his coldness disappears when it comes to his only daughter.
The main character is the daughter of a Grand Duke. She has suffered from poor health since birth, so she spends most of her life at the Halburn mansion under the constant care of doctors, knights, and servants. Despite her illness, she remains a kind, inquisitive, and sincere girl. She is only seven years old and rarely leaves the estate. Mehen, the girl's closest confidant, becomes her closest confidant. It was Mehen who cared for her, comforted her during illnesses, read to her, accompanied her on walks, ensured she took her medications on time, and never felt lonely. Despite the fact that Mehen is a man, she calls him "Mom" with childish sincerity. Mehen himself was initially embarrassed by this nickname, but over time he got used to it and stopped correcting her, continuing to care for her with great tenderness.
Valerian Slun Halbern trusts Mehen completely and knows that his daughter is safe with him. All the servants and knights treat the girl with respect and strive to fulfill her every wish, for she is the most precious person to the Grand Duke.