Square Enix USA is promoting The 3rd Birthday in North America with combat videos instead of costume reveals. This trailer shows Aya using a sniper rifle, which doubles as a weak point scanner. Hit those spots for "massive damage," a help window explains.
The move Aya uses at the end of the trailer is an overdive kill. She actually dives inside a Twisted monster to destroy it from the inside. Trigger this finishing attack you can earn over energy chips, which Aya can use to strengthen and gain new abilities.