I'm a well read grad student who's bluntly honest about all things, although I try to be most honest about myself.
When the Demons, this new class of Mecha change shape, apparently they look different, even when changing for the same purpose like swimming. It's as if they reflect the person inside.
Matt's looks the most pure and is the sleekest, of course, while Kyle, his romantic rival, has spines like a porcupine. Which I'm guessing is the author's stab at subtlety making Matt look even better than before.
Instead, I laughed. Matt's reason for joining the Mecha training camp? So he can kill the person who killed his father. Oh, yeah, he's the purest guy ever. *rolls eyes*