Definitely one of the best dramas that I have seen. I was a bit disappointed with ATHENA since I watched that first, but after watching IRIS, I can understand why they wanted a spinoff. The storyline is superb, with little to no dragging parts that can be seen in a lot of Korean dramas lately. Although some of the outcome can be predictable, much of the early storyline development will keep you on the edge of your seat, and after every episode, I wanted more(I actually didn't sleep for 2 nights because I couldn't end at some parts, hah). The cast is overall amazing, each playing their roles spectacularly. I also felt that the music fit into the drama very well, making me cry whenever there was a sad scene and keeping my eyes wide awake during the intense shootouts. I rated the rewatch at 8 just because I'm not a fan of rewatching dramas but this would be something I could watch again on a rainy day.