Driven out from his orphanage, Nakajima Atsushi wanders the streets of Yokohama on the bring of starvation. Determined to live, a chance encounter with a drowning stranger changes his fate...

Despite joining the Armed Detective Agency, Nakajima lacks conviction that he'd be of any use. Just as he's about to bid the agency farewell, a bomber takes over the agency with one of the agency employees as his hostage...!