Gau Ban is a boy who is struggling to become a "Sevalle," the strongest class of warrior in the mercenary kingdom of Guruda. Gau's elder sister, Elle Rag, is the 59th "Sevalle" and holds the honorable title of "Shadow Skill." The story develops around the two siblings, as they fight magical monsters and historical warriors. The major part of it is a battle called "Shadow Skills" that is fought with only the hands and feet. It begins when the historical warriors chant the words "We are invincible!" and obtain superhuman powers.