Someone already mentioned it, but I'll just elaborate for you. It's Persona Q for the 3DS. It's a thing where the Persona 3 and Persona 4 casts are pulled out of various points in their games (specifically, at points where you have the full cast i.e. Shinji and Naoto) to meet in an alternate dimension - and won't remember a thing afterwards, natch - and go through dungeons that are a bit more complicated than the ones in Persona. It's made by the people who make Etrian Odyssey, so the gameplay is pretty similar to that. The dungeon mapping is mostly manual with a bit of auto (you can draw in the map lines yourself, and put in symbols for various things you've seen, but the map square will change colour if you've "explored" - stepped on - it.) You get to choose whether you play as the P3 or P4 MC, and there are slightly different stories for each. There's lots of fanservice, they've Flanderized the personalities a bit (Teddie is REALLY annoying in this one,) but overall it's pretty cute.
