In the far distant future, the medieval world is overrun with mulans, mutated animals that brutally kill any living species in their path. The Study of Mulan Association, or S.O.M.A., sends two-year-old Rei to Besaid village, where his life will be filled with lies and unhappiness. He is treated as an outcast not only because of his unique powers, but because S.O.M.A. ordered everyone to shun him. Rei does not learn of his powers until the day before his eighteenth birthday, when he defeats a mulan. The next day, he waits for his assignment to a guarding post, like any other eighteen year old. Instead, Rei is not assigned a post, but is told to walk through the dangerous wilds to visit S.O.M.A., the association that appears to be the reason for everyone's survival in this brutal world. S.O.M.A. houses an underground lab, where experiments may one day lead to winning the ongoing fight with mulans. Rei meets with the two leaders of S.O.M.A., who try to make him feel at home. They tell him of an experiment they wanted to do on him so he can one day better understand his powers. But the association is lying to Rei. And piece by piece he puts the puzzle together. Rei realizes that he must one day discover his true destiny and meet the creator of the mulans.