It was virtually impossible to miss the barrier, so there was no issue with aiming, Keiko having moved on ahead and up the stairs by this point. The problem though with hitting the barrier was that, despite how many Mana Revolvers she was firing off, and slowly draining MP in the process, 6 MP to be exact with each shot volley, the barrier didn't show any wear or tear after the first hit. A 0 was present as the shot hit, a red one, usually a red number being the indication for dealt damage. This time, apparently there was no damage at all dealt as she shot the barrier. Plus keeping the Breathing Technique, if she had it up, was also an MP drainer as well. 

Still, if the two Gamers wanted to get through the apparently very tough barrier they could either try and keep smacking away at it or stop for a moment to try and think of a plan to either get past the barrier or around it.