Osu! Tatakae! Ouendan cosplayers took the stage for a game-inspired performance. Thanks to the internet culture in which we live, there's plenty of pictures and videos from the event to enjoy.
The SGCafe forums has started a thread for people to post images of the cosplayers, and although there are ample number of videos from the event on YouTube, the best two we saw were this one (embedding disabled) and this one (embedded after the break), the latter from very close to the stage but unfortunately missing the first 30 seconds of the performance.
View - Gallery
Watch - Video 1 (complete)
Watch - Video 2