Spirit only grinned and let Ferio look -- he was used to demonstrating for the students, because while he made a pretty awful teacher, he was always a willing subject. Unless it was as Stein's experimental subject, anyway.

"I started going to Shibusen when I was about ten... twelve? Resonance and changing forms has always been easier for me than others, though. My partners said it's because I'm an idiot." Maybe not the best impression to make, but Spirit was never above making fun of himself. He shrugged his shoulder, and soon the blade was an arm again.