If you want to play Idolmaster Cinderella girls : Starlight Stage, you need to use "Qooapp" to bypass the region lock.
But you also need to make a Japanese email account and create a japanese Bandai Namco account with it, so you can actually play the game.
From Qooapp you can also download the original Cinderella Girls Game, but I don't find it as fun when compared to Starlight Stage.