Great Forgiveness (1968)

Two brothers, one rich and the other a driver, act like master and servant when they're out, but like good friends at home. This dynamic gets complicated when a girl enters the picture. The girl doesn't like the wealthy brother; she's drawn to the driver. But the driver, seeing his brother's affection for her, acts indifferently towards her. The girl refuses to accept the rich brother, leading to several events. Later, a secret is revealed: the 'master' of the house isn't actually the driver's brother at all; it's the driver who's the true heir to the family fortune. Even then, the driver still treats the 'master' like a brother, and the whole situation ends happily.