DJK is a reliable late night spot since it's open 24 hours; I'd say the food and service together probably deserves around a 3-3.5 (with service always being gruff so bringing that down) but rounding up is fair given they're open all day and night. As a bonus for the night owls (and drunk owls), late night "happy hour" gets a 20% off discount.
My favorites here are the seafood pancake and budae jigae, but getting a King BBQ platter straight away is never a bad way to do this spot.