Definitely, Seo Kang Joon's acting is great in this drama. AND he's so much better looking than the main male lead.  The character is likeable, but not too sweet either.

 kfif:

The second lead syndrome hit me for the first time when Baek In Ho appeared. 

sameee

I was hoping until the end that they will make a twist and make FL end up with second  lead, but i dont know how far they can deviate from the webtoon though.  do you know of any adaptation that has a different ending?

Well, who wouldn't have "Second Lead Syndrome" when the lead looks like cr*p. 

There's nothing mysterious watching someone who realy isn't a looker and is clearly too old to be a student, judging from the deep lines around his mouth (yeah, the laugh lines... his life must have been SO funny), and after a while a young and cute boy appears. Yeah, do you wonder that you're having "syndrome" lol.

Besides Seo Kang Joon there is also Nam Joo Hyuk so basically everyone around beats the "lead" guy in this.