Ghost Girl
Go to Route 14 and walk down to Lumiose City. Once you arrive, make a right into first building. Inside, you should find two kids and a woman near a desk. Go to the elevator and emerge on the second floor. When you exit the elevator, a cutscene will begin. A Hex Maniac girl appears behind you. She'll walk in front of you (with no walking animation) and say "You are not the one...", then disappear.