Who is The Stoltz Family from The Makioka Sisters and what is their importance?

The Stoltz are a German family, who rent the house adjacent to Sachiko's in Ashiya. Their youngest child, Rumi, is Etsuko's playmate. Mrs. Stoltz enjoys Japanese culture, and she is fascinated by the dance recital that takes place at the Ashiya house. When growing hostilities between Japan and China affect Mr. Stoltz's business, the family returns to Germany.