Osu! is a rhythm game created by Dean Herbert, or "Peppy" as game users call him. It is a game of systematically placed objects mapped to the beat or rhythm of a song. The goal of the game is to get the highest score by accurately clicking the notes with a keyboard, mouse, or drawing tablet. The music from the game is most certainly anime/japanese dominated, so it would fit the whole convention theme.
Obviously there is equipment required, as someone with the program already on it that actually plays the game would need to bring their pc so that there are maps available. Also a keyboard, mouse, and tablet would need to be provided as well. I'm perfectly fine with bringing my old Wacom Intuos and maybe my laptop (though it isn't the best system, as I also have a desktop which I use more often) with me if needed for people to use as long as they are willing to not completely destroy them lol.
In terms of an account to use (as one is required to play and download maps,) Staff could probably just make one to use solely for the con. Internet is also needed to play if you want to submit scores, but it is not a necessity.
There is no gigantic learning curve or anything, and a tutorial is ready to play when you download the game. It comes as a map, so you can just pick it out of your song library instead of having to go back and reselect it. Overall, it's a great game that looks clean and interesting, and players that are new to the game or have been playing it for years will enjoy seeing it at Kumoricon.