This is a very conflicting beginning. Perhaps the heroine suffers from some kind of chronic disease and needs long-term treatment and care, which puts great pressure on their originally sweet love. The male protagonist may try hard to persevere at first, but as time goes by, faced with the recurring illness of the female protagonist, high medical expenses, and various restrictions in life, his heart gradually shakes, and he finally chooses to escape and abandon.
After suffering a blow, the heroine may fall into despair and self-doubt, but she may also become strong and face the disease alone, growing and transforming in the process. You can then design some plots, such as the female protagonist reappearing in front of the male protagonist after recovering from illness, making the male protagonist regret her original behavior; or the female protagonist meets the second male lead who really understands and supports her during the treatment process, and starts a new relationship, making the male protagonist realize how precious he has lost.
Intention: Positive and uplifting