I Transmigrated into the Attending Physician of a Frail Second Male Lead

I transmigrated into a book as the attending physician of the sickly second male lead, and was forced to watch the main characters' tangled love and hate. I knew the second male lead only loved the heroine, but I still chose to take meticulous care of him. After the male and female leads reached their happy ending, I accepted his confession and proposal. But just when I thought he couldn't live without me, the heroine was kidnapped. He abandoned me while I was trying on wedding dresses and rushed off to save her. What he didn't know was that if he ever left me, his illness would flare up and kill him.