Dramas with little or no romance

White Christmas
God’s Gift - 14 Days
The Quiz Show
The Quiz Show 2
Nobuta wo Produce (some cliche, but not played in a typical way and no romance)
Liar Game

Some romance but it doesn’t play that big of a part:
Cruel City
Kazoku Game

Some romance, but not cliche at all and more about other things:
Last Friends

I made a list of what you are searching but I only have 5 dramas on my list.
my favorites are:

Signal
Brain
Liar Game

I Remember You
Page Turner
One Litre of Tears
Missing Noir M
Great Queen SeonDeok

Angry Mom
Bad Guys
Ghost
Mama
Mother(2010)
Nirvana in Fire
Sign
The Suspicious Housekeeper
The Village: Achiara's Secret
Two Weeks

Shinya Shokudo
Mahoro Ekimae Bangaichi
Atami no Sousakan
Kodoku no Gurume
Gloomy Salad Days
River’s Edge Okawabata Tanteisha
Seonam Girls High School Investigators

I also recommend Liar Game (Korean) and White Christmas, as well as Mixed Up Investigation Agency (Evasive Inquiry Agency). If you like historical dramas, check out Six Flying Dragons and Tree with Deep Roots.

I second Angry Mom, I Remember You & Last Friends. Especially Angry Mom & Last Friends are very centred on the characters. You get to know them very well & get attached to them. Some of the characters really go through some tough stuff :(
I Remember You is "lighter" to watch in my opinion. It has many twists and unexpected things happening not only since it's a crime/mystery drama, but also because it's a really good crime/mystery drama! (I mean a lot of these crime dramas are still quite predictable, but this one keeps the suspense really going.) The characters are also quite interesting.