Shin'ichi Kosaburō is a fifth officer with the Tokyo Police Department. After Kujiranami Hyōgo escaped from his cell and began rampaging with a grenade launcher, Shin'ichi - like his compatriots - is at a loss for how to deal with the disaster until Myōjin Yahiko intervenes with a plan and the courage necessary to win. Though frightened, Shin'ichi gives front line support to Yahiko and rallies the other officers to help subdue the behemoth. By the end of the series, Shin'ichi has become a student of Kamiya Kasshin-ryū at the Kamiya dojo.