Japanese Express is one of my top dining spots when I somehow end up in Pacific Mall. It's located at the 2nd level near the back of the mall (pass the mini bridge with the pond). It's the only food stall with it's own seating area.
Their bento boxes are very good quality for the price you pay, but my absolute must-order is their Japchae which they sell by the pound... dare I say, it's the best Japchae I've had!
It's cash only and there is rarely a free seat in the food court, but I'll eat standing up if I have to... or just get take-away.