Kakurenbo is a 25-minute anime short done by Yamatoworks that won critical acclaim at several animation festivals. The style is very CP, so I thought I'd link it up from YouTube.
The plotline is as follows:
Among the ruins of the city, there is a game only children can play. It is called �Otokoyo�; a game of hide-and-seek. But whenever children play this game, one by one they would disappear into the blinds of the buildings� The story begins when a boy enters the world of Otokoyo, to find his missing sister.