While at the beach, Yui, a high school student, came across an unconscious boy who went by the name of "Sid" and whose true identity was unknown. After confronting the locals, it was revealed that Sid was one of the Uncanny Brains, a group of humans created by the Japanese authorities as weapons. With Sid's incredible abilities coming to light, Yui and her companions must consider whether his arrival on the island will lead to disaster.