Rin instinctively took the rear entrance in case the guards from 29 doubled back around through room 18/19. As he stated before, the lower route may be less guarded for a reason and one can't factor out that they didn't buy the changing ones mimic. Jumping up above the girders supporting the low hanging celing lights he held onto a nearby I-beam while planting his feet horizontally. Keeping himself flat above the rear entrance ready to pounce down at a moments notice. Keeping his blade pointed downward with jaws wide open waiting like a mantis stalking his prey. 

A low gutteral grow followed by some clicks signaled to his teammates he was ready. (Ha! Teammates!) the thought of the word tasted sour in his mouth. He trusted them no more than he would trust these guards. If anything, he's eaten bigger things than the ugly-fleshy one called Liz. Although that tan flesh looked rather tasty hmmm....