Airs Blue

Appearing much older than he really is, Airs Blue is the leader of Team Blue, and at one point, Captain of the Ryvius.

Skilled in martial arts himself, Blue intentionally puts himself in danger so as to feel alive. He was suppressing his violent side when on the Liebe Delta, but the Ryvius is a whole new environment and Blue sees the opportunity to unleash his natural aggression and take over the ship.
The fact he owns the only firearm on the Ryvius, a needle-shooting pistol stolen from one of the saboteurs of the Liebe Delta, assists his coup significantly.