One of the best I've watched. Easily a 5 but some things are unrealistic even for a fictional K-Drama.
(A bit of spoiler) For example, the 4 counters are working in a noodle shop, with a billionaire counter financing them. The villains know where the counters are, and they can't devise a decent plan that works in their favor. The counters should have worked in a secret, less obvious location and not rely on erasing memories every time. A disguise of some sort would have really made more sense. Running around in red attire even at night is too obvious with CCTV all over the place. Good thing the villains are not too tech-savvy and don't employ anyone who are too evil to use a gun. ๐
Nevertheless, I like the story and enjoy the unique plot.