Basically, staff of toys’ r us and the pokemon centers in japan will trade you a Scyther or Haunter for any pokemon. Those pokemon evolve as they are being traded and also mega evolve with their proper stone. If you also bring BW2 you get a lucky egg serial code.
I wish the Pokemon Company International could really get to work in these for everyone…. I felt XY could do that since the international release, but they haven’t.