Jae-Gyun Hwang was born on July 28, 1988 in Seoul, the capital of South Korea. He attracted attention as a teenager, and was drafted straight out of high school. The Hyundai Unicorns selected the youngster 24th overall in the 2006 KBO draft. He made his professional debut in 2007 as a 19-year-old and hit a respectable .300/.323/.375 in 171 plate appearances.
Over the 2008 offseason, the Hyundai Unicorn franchise folded, and in their place the Woori Heroes were born. Issues between Woori Bank, individual team owners (a rarity in Asian sports, where teams are generally a subsidiary of their corporate sponsors), and the KBO led to Woori breaking the naming deal in the middle of the season.