In a world where humans can coexist with a group of beetles that have separated from the earth, and are each other's sworn enemies, humans can only live in suspended animation in the air. Inside the city. The instinct of human beings is survival of the fittest, so in order to fight against the magic beetles, human beings have also born air combat mages who can use magic power. Sando Yingsi studied at the training school for air combat mages - Mistgang. He is the ace of this special agent team. He was once known as the "Black Sword Master" at his peak. But now, because of a misunderstanding, he became a traitor of the secret service team. He was disgusted and despised by everyone, and was appointed by his superior as the instructor of the E601 team, which had lost consecutive battles. The members of this team are three girls with weird personalities, including Ruikudi, who is naturally timid, Misora, the team leader with a sense of justice, and Riko, a very smart but naughty girl. They are now the so-called A combination of a traitor and a problem girl, then let's see how the four fight back against those who look down on them.