Kain Fuery is one of Colonel Roy Mustang's direct subordinates. His rank in the military is sergeant mayor and he's a communications expert capable of wiring anything, anywhere. Never doubt his smartness.
But Fuery is above all, a kind person who cares deeply for his comrades. He's probably too sweet for the military work, even. But that's balanced by his strong willpower and braveness on the field.
It's also common knowledge his liking for dogs, as he is the one responsible for Black Hayate's integration in the team. And how much we all love him for that~
When Roy gets assigned to Central, Fuery's one of the few people he chooses to acompany him. Well, Roy can really choose his personnel, don't you think? I better stop before this turns into Roy!worshipping.