The Little mermaid

The story centers on the youngest mermaid princess, who lives in an underwater kingdom with her father, the Sea King. Fascinated by the human world, she saves a human prince from drowning during a storm and falls deeply in love. To earn an immortal soul and win the prince, she makes a deal with the Sea Witch. She trades her voice for human legs, knowing that every step she takes will feel as if she is walking on sharp knives. 

When the prince marries another woman, the little mermaid is destined to dissolve into sea foam at sunrise. Refusing to kill the prince to save herself, she sacrifices her own life and transforms into a “daughter of the air,” a spirit capable of earning an immortal soul through 300 years of good deeds