Fantasy Maiden Wars is a Touhou x Super Robot Wars crossover created by Sanbondo; using the characters from Touhou Project created by ZUN.
In Mission 10; you're supposed to be fighting Sakuya, but Yuuka shows up to watch. Alice, Reimu and Keine all tell you not to provoke Yuuka.
Naturally; you can actively provoke her. And this is what happens when you do. After you provoke Yuuka; she'll stop 'observeing' since Marisa fires her up. And she'll start actually attacking your group, and using MAP attacks to boot.
Of course; you can work around this by timing the attack for when you're about to finish the main objective [Defeat Sakuya] on the same turn.
