Mamoru secretly protects the troubles that occur around Ponya Yuuna from the shadows. When she was just in her second year of high school, such a daily life would no longer continue. Surprisingly, Yuuna has been targeted by the villainous Kadōzaemon, the leader of the villainous group! Mamoru joins the villainous group to protect Yuuna. With the words "I've been protecting my neighbor for 400 years", I quickly defeated Hidōzaemon and thought the case was over...