The予告 of revenge against Jeon Hye-jin is making it even more interesting.

Na Byeong-mo said he would punish him, and asking if he could pretend not to know as an adult, he let Hwang Jun-hyeon go.
He was asked how he would take revenge on Kang Jae-kyung. To this, Hwang Jun-hyun replied, "I will hand over the hydrogen technology first."
There are plenty of other things to bring besides that. While answering Kang Jae-kyung, he acted as if he was on Na Byeong-mo's side!