Keisuke is a nice guy to be friends with. He is that one person who would seem to serve as some kind of eternal bodyguard to his fellow Scarf Heroes (especially to his sister, Suzuka), and doesn't really ask for too much in return for all of this, just as long as he and his friends can make it out of situations in one piece. He has his flaws, however, in that he's way too hard on himself when he makes a mistake. That, and he may be angered to the point of activating "Overkill Mode", a mode in which Keisuke is so enraged that he cannot think straight, and will not return to his normal state until he gets even. Keisuke generally does not show as much fear as a human (for instance, walking casually in a situation in which one may be panicky), as he lacks various weaknesses humans have and is highly resistant to magic and energy based attacks, but Keisuke is quite heavier than a human. If he does fear SOMETHING, he's usually incredibly frightened by it. Keisuke usually fights defensively as opposed to aggressively (Suzuka is the aggressive fighter).
His main strengths are the fact that he possesses one of the few weapons with hyper attacks/limit breaks/whatever you call them (other characters whom bear arms with these include Richard and Suzuka), and that it works well in pretty much any situation. He also is highly resistant to magic and energy based attacks. He's pretty heavy too, but that also happens to be one of his weaknesses at times as well, and is essentially a lightning-bruiser type character, focusing more on armor, and is one of the sturdiest characters in the series.
As for his role, Keisuke serves as an engineer and one of the two main vehicle pilots, the other one being Richard. Keisuke is particularly good at making sharp turns and drifting around corners (and eventually off-road pursuits when he switches to the Horizon Hunter), but his vehicles usually aren't as fast as those driven by Richard or Eggurai. Whilst being a serious character at most, Keisuke still has his moments.