I haven't watched them but I think he was a lead in Welcome to Wakiki

I think he was recurring character in Descendants of the Sun

He was brilliant in Children of Nobody. Not the usual type of roles I know him from (there was no comedy at all) but he delivered 100%on the complex and understated emotions of his character. And he was one of the smartest policeman we get to see in K-dramas.

Typically, you get completely moronic police characters who can't come up to their own conclusions because they're written to make room for the main character (who, here, is portrayed by Kim Sun-a). It's not the case here, and you get a sensible, smart, and compassionate policeman (and his points make sense 100% of the time! I loved the character, he was so brilliantly written).

Also, it's another excuse to watch Na Young-hee working on her bad mother antics (as per usual; the woman seems to be typecast into bad mom roles)

The first drama of his that I saw was School 2013 where he played a character named "Lee Yi-kyung." The School series is known for the students using their real names. School 2013 is hands down the best season in the School series (after its revival in the 2000s), so watch it. A lot of big stars got their start from it, so you'll recognize some of the actors.

Children of Nobody was definitily is best role! I wish to see him more in roles like this one.

He's kinda typcasted in funny roles. He's good and he has a good timing in comedy and body comedy too.

He was funny in Descendant of the Sun as a young man stuck under a building or in Welecome to Waikiki.

welcome to waikiki. he is brilliant is whatever he does though. children of nobody was so great too. But him and rebecca will always have a place in my heart (watch waikiki)

He has a cameo as a doomed astronaut in space disaster movie "The Moon".

He was fantastic in Children of Nobody, but I regret everything about that show except him, so I'm not gonna recommend it.

I LOVED him in Nine: Nine Times Travel.

He was very funny in the fantasy sageuk Mirror of the witch. And he wore a mane of glory.

I loved that drama, which maybe is too dark and creepy for some people, but there are comedy elements too.

If you want a young version of him My First Time is a light fun show. Other male leads are Choi Min-ho and Kim Min-Jae. It’s about 6 friends in their early 20’s trying to plan their lives. He also plays a small role in My Love From the Stars but while the show is so great, his role really wasn’t.

So he's absolutely hilariously excellent in Welcome to Waikiki, one of my favorite comedies. Park Sung-woong has a hilarious cameo role in the drama, and he and Lee Yi-kyung reunited in the funny movie Bear Man, which I also recommend!! (Available on Viki US)

I'm not familiar with him, but I see one of his early roles was in You're All Surrounded, which I enjoyed.

He kept it under wraps until his very successful father retired from being the CEO of LG Innotek. If you have had an LG phone- that is the company that made it. I first saw him in WELCOME TO WAIKIKI but perhaps his best acting was in CHILDREN OF NOBODY and the recent MARY MY HUSBAND.

If you like dating shows he is one of the commentators on the very successful I AM SOLO.

He’s also a prolific instareel poster and it is hilarious. I see him more there than anywhere.
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Everyone's already said it but I honestly LOVED him Waikiki 1 & 2 so here's one more comment to emphasise that fact. The strength of the first season especially lay in how elite the comedic timing between the ensemble cast was, but LYK was laugh out loud, side splittingly hilarious in particular (and endearing??? I was tearing up in those scenes where he finally gets his 'big break' in the industry and stuff).