If asked to pick one costume that completely defined 2010 for me, it is this one:
While there have been many cosplayers of Touko/Hilda/White since, this photo was taken just two weeks after the first pictures of the protagonists for Black and White were leaked onto the internet from CoroCoro magazine. I was the first cosplayer outside of Japan, if not the first cosplayer period, to complete and wear this costume.