Okay first things first, you have to watch this drama it is awesome.
That having said I should start to explain so more details. I saw the trailer for this show about a week ago and even tough there are a lot of other dramas, wich I am currently watching, I felt, that I needed to watch this one as soon as possible. And I was right.

The story develops with a constant speed but always focused on keeping the viewer, so that everyone understands what exactly is going on. At first I was a bit worried about having the same actor playing the two male lead characters. But the way he does and how the special effects in this drama support this is awesome. I have to admit that I couldn't really decide which male lead character I should ship with the female lead character, because they were both way too cute. A huge shoutout to Yoon Hyun-min for portraying this two characters.
Personally I really liked the scenes in wich the two male leads were talking to each other (I mean just think about the huge amount of editing and acting, having one actor in one role shouting at himself, while the other role stands right in front of him being calm, like nothings happening).
The female lead character is really adorable and thankfully not one of those "is getting dangerous you need to protect me"- characters as she faces a lot of trouble by herself.

Okay maybe I should tell you something about the actual plot:
It all starts out with this fancy glasses, which create an holographic KI being introduced by an (IT) company. Of course having such a futuristic objet makes a lot of enemies. So what can be done? Of course (like in every good drama) involving innocent people in this mess and create an even greater one.

I think, I have said enough so - you need to watch it. :))