Ao Fukai is a 13-year-old boy living in the year 2025 in Okinawa on the island of Iwato Jima with Dr. Toshio Fukai ever since Ao's mother Eureka disappeared 10 years ago. When a mysterious organization attacks the local Scub Coral, Ao somehow gets mixed up in the battle and manages to activate an enigmatic robot called the Nirvash while it is being transported by the Self-Defense Forces. Later, Ao finds out that the Nirvash belonged to Eureka, and embarks on a journey to find his mother and learn the truth about his origins.