"Kaisuke is the mechanic of the group, and as well as the other members of the Capsules, he is openly defiant to authority and has little regard for pedestrians, showing how he curses the oncoming wave of people running in the opposite direction while he was trying to drive on his bike.

Despite this, he is one of the softer, less volatile members of the group (unlike Kaneda, who is arrogant, and Tetsuo, who has an inferiority complex and an explosive temper,) and cares deeply about his group. He is shown to be bursting into tears when he sees that Kaneda survived an incident." -Taken from the Wiki

Kaisuke's voice should be more boyish than the rest of the Capsules, as he is the youngest and newest member.