A main theme of the series was the  power of investigative rights. Should the police have the power to close investigations? I am unsure of my opinion. On one hand it can be dangerous for one entity to hold so much power but on the other hand, as someone mentions in S2, giving the power to the same entity that starts the investigation seems more  that they would be more likely to convict innocents.

What are other peoples opinions? (please keep it respectful but I would like to hear earnest discussion!)

i share si mok's opinion in regards to this. the prosecution having the power to indict and investigate is correct. warrants infringe on human rights and the police, who don't study law, aren't qualified to make those decision. not only that, the police force is like 100 times the size of the prosecution. if the police could in fact request warrants, where on earth are you gonna get 100 times the current number of judges from?

what needs to happen instead, is a reformation of the prosecution system. in the prosecution, disobeying your superior is insubordination and you can be fired for doing so (i think this is still the case?). this was implemented so that the prosecution could work as one unit moving towards the same goal more efficiently, but it is also so obviously abusable its laughable. i mean how can there be check and balance if the ones with power are all untouchable? it's just begging for corruption to happen

If you want to read discussion about this drama and related topic, check out Dramabeans recaps Forest of Secret 2 . The comment sections are full of intelligent discussion about this drama. 

If you are interested in finding out more about the investigation right debate between police and prosecutor in SK,  here are the links posted on Dramabeans. Apparently Parliament has passed a bill regarding this issue in January 2020. 

http://m.koreaherald.com/view.php?ud=20190709000553

http://www.koreatimesus.com/parliament-passes-bills-to-rebalance-investigative-power-between-prosecution-police/