Sio Ogura visits Taiwan with her class on a school trip. However, things change for the worse when strange creatures called “Evolutionary Invasion Objects” (EIO) appear out of the ocean, and when a young man named Jack appears to cut them down with a massive blade. He is injured when one of the EIO stabs him in the stomach. Sio sees his AU ball and remembers her past self, using it to activate “Nobunagun”!