I've watched a few of the same themed Korean dramas. At no point do I feel Lee Seung Gi is acting a part. Where I often commend actors at the exact moment that I am moved by their interpretation, Lee Seung Gi's acting is immersive that I forget it's a drama. The feeling of it being very natural is primarily the reason I want to give the show the highest rating.

I've watched a few detective-themed Korean shows as well and I must say Mouse has the best utilized team. There is always a character of a cool chief, the slightly clueless but useful sidekick, the rat, the dependable detective, the rival, the ex partners, the detective that crosses between good and evil, with compelling reason. The cast are memorable and even though they fulfill the said character roles, their acting doesn't lean on cliché exaggeration.

Onto the more faulty parts -

The storytelling comes to an abrupt disconnect in the middle. From a cohesive narrative episode by episode it's as though an unrelated arc is suddenly introduced. That wouldn't have been a problem if presented more smoothly.

I am also not a fan of the scientific fiction but I give merit to the idea. I'll leave the morality discussion to those who are interested.

From the reviews across platforms, I've noticed the mother isn't criticized enough. She is more concerned about assuming the sin for the son rather than feeling sorry for the circumstance she maneuvers that allows him, them, to turn out the way they have. The pd lady is another character with useless lines. Aside from her program being too convenient for the plot, she poses herself as a significant character with moments of taunting the "father of all psychopaths" in the show but actually doesn't do sht -- and I'm glad it is other two characters who actually are given essential parts in the end in relation to the main character.