Oh, something I should mention. I know not a lot of the characters so far actually use magic other than Arlo but it's something interesting to know regardless.
You can force your body to take in more mana than it can hold, but if you do it in excess you'll disintegrate.
Kaite has limiters and capacitors wholly aware of his abilities.
While he always functions at 100%, that is all he is capable of, with that understanding.
EDIT: Kaite's Cannon feeds off of mana.