Treasure: The Irreplaceable Thing I Found

Kevin Caro toils as a young miner, swinging his pickaxe and sweating.
He spends his days gloomily, troubled by repaying his father's debts. But one day, he finds a girl washed up by a river he stops at and takes her home to nurse her back to health.
The girl—a bold and spirited self-proclaimed thief named Willie—thanks Kevin for saving her.
But she becomes disheartened upon realizing she's lost ‘a ring stolen from a certain place’.
She somewhat forcefully decides to stay at his house while searching for the ring.
Kevin's life is turned upside down by meeting this girl.
He is tasked with investigating an underground dungeon found in a mine. Unexpected trouble leads them to have sex (for the first time for both of them). They misjudge the distance between them and fight, then make up with sex. They go on dates to the beach...
The days spent together under one roof bring them closer, and eventually Kevin and Willie become special to each other.