The premise itself is pretty interesting and the backstories of each character are well established and play vital roles in the story. The first few episodes that lay down the groundwork are fine but towards the later part, the story kinda becomes a mess and kinda hard to keep track of all the cases/investigations going on.
Personally I find the director's or writer's decisions pretty questionable as they lead to multiple plot holes or rather "plot-conveniences" which are kinda outta nowhere.
The drama kinda tries to portray the ML to be somewhat of a genius. But following the events of the drama it's pretty clear that he's nowhere near that status. Instead he frequently endangers his allies in some gamble that has extremely low odds of happening, yet they happen (plot convenience lmao). He also doesn't take the antagonist seriously enough even though he's evil af and can kill anyone without batting an eye. The ML takes multiple Ls yet never actually mends his ways to prevent past mistakes.
Also the drama tries too hard to portray the nephew as some sort of important character even though he is the most underachieving person in the entire setting.
The ending is clearly rushed with the absence of any real climax. The good guys beat the bad guys within just a few minutes and nothing much is shown as how they did it or any buildup whatsoever.
Overall the drama begun as a promising one but went downhill and never recovered. The music was nothing much memorable. Perhaps acting was the strongest point in the entire series.

I wouldn't recommend watching this unless you have waaaay to much time to spare or are a big fan of any of the actors.