This guy also sounds like Ji Chang Wook when he talks as well as the facial expression. I am confused since there is nothing online about it nor is there a casting for this guy

This should be signal. Actor Lee He Hoon from Singal and the taxi driver.

It’s neither.  It looks like Lee Jung Woo who is listed as unknown. But I can’t be sure. What i’m sure is that that actor is neither of the two you mentioned. 

Sorry it's Lee Je  Hoon Try Google search using the sentence in the picture below . The other looks like Lee Yoo Join and Choi Kyung Gu.

It is not Lee he joon . Check the soompi article about the cameos. If he were in episode 5 as you say, he’d be listed and everyone would be gushing about him. 

And after a search, it’s https://asianwiki.com/Jang_Young-Hyeon_(1993)

Do a google dearch, you’ll recognize Lee him. 

Thanks I was so confused. I appreciate it😁🙌🏽

Thanks I can finally feel assured and not confused