Gunner is one of the many classes the boy mastered on his way to completing the onion knight class. So Ribbon protects him from her status effects.

And everyone else focusing on her gives him enough of a distraction to move to stage two of his plan. Now that he's behind her, his attention turns to Garland.

"Don't think you can just walk away you coward!"

And with enhancements from Dualcast and In the Red he drops the crowning spell of the Black Mage class on the retreating Garland. Twice.

"Ultima!"

The Onion Knight also has one more little surprise for his opponents, but that will have to wait.