The Attack on Titan is a popular manga which has been doing the rounds in Japan for over a year now and recently made the transition to anime which debuted in April, 2013. There is also a Titan iPhone app which received an overhaul to coincide with the release of the anime.
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The app allows you to overlay images from the series into your surroundings so this past weekend saw an Otaku bring it to the holy land of Akihabara. Harmless havoc was unleashed judging by the pictures in the gallery.