Genki comes off as a friendly and pleasant guy when Shōya first meets him, but that quickly changes after Shōya punches Genki's younger brother for stealing his shoes. Genki retaliates by uppercutting Shōya in the gut the next time he sees him, leaving Shōya covered in bruises after he is lifted into the air by the punch and lands flat on the pavement. At this point, Shōya’s sister had moved on to Pedro, so Genki isn’t seen after this.

I don't have a set voice for him, but please do make him sound like a male young adult!