This hero action series depicts the further exploits of Z-END, who, despite being called the strongest and most evil Knockers, fights for justice. In 2010, middle school student Kawachi Taishi, worried about his missing Knockers classmate Shingo, accidentally finds an email address leading to Z-END, who secretly solves cases involving the Knockers. When Taishi goes to the location specified in the reply, the Hound Inn, he meets Akari Choji...!?