The father is very traditional, wearing a gat, while his son is more modern, having learned how to make money off of the "long-nose" American soldiers (by shining shoes and leading them to "Shibi-Shibi" girls—prostitutes—to be serviced), going so far as to adopt parts of their jargon.
The father, angered and frustrated by the lack of respect being shown to him and his heritage, chooses to walk back to Sango Po, telling his family to take next day's train.
The dog's condition worsens, and the boy wanders a nearby town, which is filled with churchgoers and "Shibi-Shibi" girls pairing with their American lovers.
He tells the couple a story about the origin of the gat - explaining that the garment was intentionally designed to be delicate and easy to knock off so as to deter men from fighting.
[1] It explores the breakdown of traditional Korean society, as seen with the disrespect shown to the father, the need-driven willingness of the mother to be exploited, and the amoral, war-driven entrepreneurial dealings of the boy.