The Canary Who Became the Cure

Raised in a foster home, Ivy signs a ten-year contract with heir Ethan, who can only sleep beside her. She thinks she is special, only to learn she is a stand-in for his first love. When the contract ends, she leaves after he gets engaged.

Without her, his illness worsens, and he realizes Ivy saved him from a fire. Full of regret, he wins her back.