I just got Persona Q2 on my 3DS earlier this morning; I have a few long train rides coming up, so I figure it will be a good game to play on those at the very least. Plus, the trailer on the eShop gives me the impression that it initially focuses on the Persona 5 cast, so it should be a good jumping-on point for learning about Persona 3 and 4. (though it just hit me that hopefully there aren't any gigantic spoilers for those games in here)
However, I find it weird that the game is rated M, considering that every single thing about it makes it seem like it's intended to be a kid-friendly spin-off for the Persona series.