I'm personally betting on Neo. Pretty sure she was the one that cast the illusion during Em and Merc's fight with Coco and Yatsu. Most likely Neo placed an illusion on Yang to make her think she was being attacked, when in reality nothing happened. That's why the cameras show her just hitting Mercury. Also, another note. Ironwood said he thinks he knows how to transfer Aura, so I'm wondering, whose Aura did he take to give to Penny?