I enjoy a good rhythm game, and although Sega has put out quite a few over the years I don't seem to have sat down and played through very many of them. (The last one I can think of playing was the Wii-make of Samba de Amigo, which I played more than a decade ago!) I'd heard good things about their 3DS rhythm game Rhythm Thief and the Emperor's Treasure, and I've been playing it off and on. I finally finished it today, and although the game is enjoyable, there's not a whole lot to it. As many reviwers have noted, the game has a very Professor Layton-like presentation, although not as warm and compelling. The story is pretty standard fare, and although there's a decent variety in the types of rhythm games, every mechanic reappears several times so by about less than a third of the game's seven and a half hour's running time you'll have seen pretty much everything the game has to offer.
As with the aforementioned Samba de Amigo, in this game you have a meter that determines what your end rank is, and each stage is divided into three sections, and if you make just one or two mistakes in the final section you can quickly drop from an A down to a C or lower. I was able to pass every stage with at least the lowest rank with minimal effort and retries, which was fine with me, although people looking for more of a challenge would have to wait until they beat the whole game once, after which a hard mode for each stage unlocks. The game features a couple of extras, like single-card download multiplayer, and you can always go back and replay any stage to chase after a higher rank. Post game apparently there are also three bonus chapters, each with their own bonus stage. You earn each of the first two by finding all of a certain type of collectable within the game, and the last one unlocks when you get an A rank in all of the normal stages.
Overall this was an enjoyable game, particularly for fans of rhythm games. The references to previous Sega rhythm games (including Space Channel 5 and Samba de Amigo) were fun, and although this isn't an essential game in the 3DS's library, it does fill a particular niche and any rhythm game fans looking for something to play should enjoy it.