Yes TCAS is not accurate in azimuth but we are talking about plus or minus a couple of miles here. When you are travelling at around 5 to 6 miles a minute on a descent a couple of miles is very little. Japan airspace is very busy and you are constantly being passed from controller to controller as you descend in to lower airspaces therefore the initial post is very relevant. There have been many TCAS incidents in Japanese airpspace and there are likely to be many more.