To the south of Japan lies the lush green island of Southern Cross Isle. One night, a boy named Takuto Tsunashi washes ashore after swimming alone from the mainland with nothing in hand. He enrolls in the senior high level at Southern Cross High School, where his bright and positive personality quickly earns him friends among the students, including Wako Agemaki and Sugata Shindou. However, the school harbors a deep secret: beneath the ground lie sleeping giants known as “Cybodies.” About twenty of these giants exist, and they are just some of the many mysteries hidden by everyone on the island.