I have a terrible concentration problem, and i give up on dramas waaay too easily. sometimes even within the first 20 minutes. i once gave up on secret garden  after 5 episodes because it bored me but i went back 5 months later and it became one of my 10/10 Dramas

i'm in my"watching kdramas are the only thing i want to watch and do in my spare time" and really desperate to watch another BUT after recently finishing signal it became the greatest kdrama i have ever finished heck it's the greatest drama i've ever seen period. it has set the standards way too high. It had me hooked from the first 5 minutes and it was the quickest i've finished any drama.

Secret Garden made it difficult to get into romance but signal seems to have gone one step further and made it hard for EVERYTHING. I keep trying to start a new one but because of not just how amazing signal's FIRST episode was i keep giving up quickly everytime i start a new one :( help

Maybe you'd like Nine Times Time Travel. It's intriguing and you keep wanting to figure out what happens next. It's a little confusing in the beginning though, if you get bored waiting to make sense of things.
Missing Noir M
Bad Guys
The Master's Sun
+10000 bad guys
three days
vampire prosecutor
triangle (but it gets a bit draggy towards the middle)
cruel city (takes about an episode to get in it, but once there addictive and climax builds and builds)
mask
love me if you dare (its Chinese, but very addicting, really worth a shot if you are into investigation, mystery, murder, romance, loveable characters, and great acting)
I second Love Me If You Dare. It's really good and I think it's the best drama to watch right now ;) As soon as I finish it, I think I will add it to my favorites!
Remember – War of the Son
Kill Me, Heal Me
Good Doctor
Angry Mom
Boku no Ita Jikan
Ouroboros
Orthros no Inu

All of these are really great dramas!
Remember - War of the son did the trick for me... tho now am too addicted to that one xD
but ye recommending that

I also recommend:

Special affairs team TEN +++
Missing Noir M +++
Love Me if You Dare +
Bad Guys +


The infamous drama slump--we've all been there! This doesn't exactly answer your question, but I suggest you try something completely different from Signal. Try watching a movie, or a Japanese drama with a loose episodic format, or a short drama (e.g. Splash Splash Love, Page Turner, or Nightmare Teacher). And maybe choose something that doesn't require too much emotional investment? (A comedy drama, say.) I think that might do the trick rather than trying to find the next best thing after Signal. Good luck!
After Signal i watched Nirvana in Fire but thats obviously not a K-Drama (as you have specifically asked for k-drama)

Only ones i can really recommend is Cruel City, Bad Guys or Secret
I also recommend Liar Game!
all the recomendations here are a+ ,
i recommend white christmas  it's pretty much a classic