Some info we've got so far:

• Created by QualiArts, company behind IDOLY PRIDE and Gakuen Idolmaster.
• Simultaneous JP and Global release.
• 50 talents, everyone currently active minus FlowGlow and Justice.
• 150 songs on launch, 2 per talent. Will include both originals and covers.
• Hard and extremely hard difficulties.
• Auto mode for those not interested/unable to play rhythm games.
• Custom chart (beat map) editor, option to share your creations with other players.
• Talent card gacha.
• Paid skins.
• Option to play with MV or 3D Live background.
• Story mode (will include some talents who graduated during development).
• Skill tree for talents.
• No release date as of now.

The first trailer seems standard Rhythm game gameplay, but in the second there’s also an Island (?) so I guess it’s going to have a sim component or at least some cutscenes

user created charts are awesome, I'm excited for this release :-)