Two of South Korea's top-grossing filmmakers and a major distributor have entered the microdrama market, the latest sign that the country's entertainment establishment is treating the fast-growing short-form format as a serious business rather than a passing novelty. Lee Byeong-heon, the director of "Extreme Job" (2019), which sold 16 million tickets to become the highest-grossing Korean film ever, premiered his first microdrama on Feb. 4. "My Baby Daddy Is My Guy Friend" (working title) was rel