You would think this is a stampede caused by some crazy discount sale in Takashimaya. But it isnt.
This crowd is, in fact, split into two factions - one trying to get to Takashimaya and one trying to get out. It so happens that they meet each other at the entrance of Isetan.
Each is as strong as the other, so it is an impasse. Smart people (like me0 from either crowds abandon their positions and run inside Isetan and get out of the tunnel and brave the torturous rain that is pouring outside. Others, stay there and test their body strength by trying to push their way through.