The movie is the latest South Korean film to pit the haves against the have-nots: see this year’s No. 1 movie there, “Extreme Job,” as well as recent titles like “Burning” and 2013’s “Snowpiercer.” It’s no coincidence that income inequality is a recurring theme in the nation’s cinema. Experts say the films, for the most part big hits at home, capture the essence of Korean sentiments at a time when the country’s income gap continues to widen. South Korea’s income distribution is remarkably lopsided. In 2015, the top 10 percent of South Koreans held 66 percent of the nation’s wealth, while the poorer half of the population held only 2 percent.