Well that's surprising. Square Enix announced today Idol Fantasy, after some trademarks popped up last week and it's a... "magical heart-throbbing fantasy x idol training game" which basically means that you'll be managing a boy band but they all come from a fantasy world.
It seems to feature plenty of dialogues, dancing and each "hero" even has a 2D sprite form. They'll be designed by legends like Tetsuya Nomura so there's a lot of talent behind this crazy, typically Japanese game.
It'll come in Japan this summer to iOS and Android, and we'll see if Square wants to localize it worldwide.