The product of natural selection has resulted in the creation of a new and deadly species called "Eclipse" with the sole purpose of annihilating humanity. Leading a group aimed at combating these lethal bone creatures was a scientist named Kurusu Kenji. He developed "Osteon," creatures similar to the Eclipse, that respond to the orders of the human from whose DNA they are created. Sadly, Kenji has disappeared, leaving his assistant Kidogawa Rokuko with the tedious task of recruiting his long-lost teenage son. Kurusu Akira, who had no attachment to his father for he believed Kenji had deserted him, was reluctant to join the organization. However, an attack from the Eclipse forces him to accept his own Osteon from Rokuko. Eventually, Akira becomes more involved with the group, and though he and his Osteon have little interest in safeguarding humanity, they are determined not to surrender. As members of the organization expect him to take his father's position, Akira's resolve is put to the test.
