That acting coach is none other than fellow ZE:A member and actor Siwan. In an interview with OSEN that progressed the other day, Hyungsik said, "I normally exchange talks with Siwan on acting. But it's not any kind of serious, pompous talk where I ponder, 'Hyung, you know that thing called acting?' But we naturally get to talking about it, exchanging questions and answers." 

Hyungsik continued, "I think we help each other out through our acting. There are many times I seek advice from Siwan. I ask him, 'Should I approach this emotion this way?' and Siwan would answer, 'I think you should do it like this,' and offer me a lot of help. One time I saw Siwan reading a script and he handed it to me telling me to read it. We read each other's scripts and practice our lines in different tones," explaining how they share with one another their expertise on acting.