As far as I can tell, there are about eight base set cards for Hwang among the well known KBO issues of the past few years. He had a card in the 2010 KBO "game" set and also appears in base sets of the 2014-15 Blue Edition, 2015 Season Two, 2015 Hell's Fireball, 2016 Diamond Winners and 2016 Forever Ace sets, all from Super Star Baseball (or whatever the company is actually called). He also has insert/short print cards in Super Star Baseball's 2014 Season One and Three sets and the 2014-15 Blue Edition set (in addition to the base set cards), autograph cards in the 2014 Season Three, 2014-15 Blue Edition and 2015 Season One sets and (I think) a patch card in the 2015 Season One set. You can see a list of these (including some parallels) here.
Here's the cards I have from this list:
|2010 KBO "Game" set #AN-007|
|2014-15 Super Star Baseball Blue Edition #SBCBE-159-GN|
|2014-15 Super Star Baseball Blue Edition #SBCBE-177-GN|
|2015 Super Star Baseball Season Two SBC1502-111-N|
|2015 Super Star Baseball Season Two Sticker|
|2015 Super Star Baseball Hell's Fireball #PA01-LO006|
|2016 Super Star Baseball Diamond Winners #PA02-LO001|
|2016 Super Star Baseball Forever Ace #PA03-LO004|
And I don't know why this hadn't occurred to me earlier, but I had actually seen Hwang play in Arizona last February in the game Lotte played against the Hokkaido Nippon-Ham Fighters. He was the one Lotte player to get a hit against Shohei Ohtani. Here's the tweet from @MyKBO that reminded me:
Here's a GIF of Hwang Jae-gyun's single off of Otani today in the 1st inning (via https://t.co/Gvhd4vBGqy) pic.twitter.com/OQryeBUqdd— Dan Kurtz (@MyKBO) February 11, 2016
You can almost see Deanna, @the_hereford and me behind the Fighters' dugout (the Padres' side).