Floating Clouds (1955)

This film is based on flashbacks, which I'll ignore here for the sake of clarity. Married Japanese forester during WWII is sent to Indochina to manage forests. He meets a young Japanese typist and promises to leave his wife. He doesn't and after the war, she turns up and the affair resumes.

He, who is a womaniser who takes women for granted, is cold, uses her for occasional sex and takes other lovers. She, while forced to become a mistress of a GI when she can't get a job, loves him and cannot give him up, even lending him money. In poverty, she becomes a mistress of a rich man, but gives him up when she cannot forget the forester. When the forester's wife, whom he never leaves, dies of disease, the forester takes a job far away. Despite his lack of interest, the woman, who is being pursued by the rich man whose money she stole, comes with him. Becoming ill on the journey, she continues with him, rather than rest and recuperate, obsessed by her constant fear that he will leave her. As she dies, he realises his mistake in rejecting her perfect love.