Having just been orphaned, 10-year-old Marina Von Edelschwarz has inherited her family's back country estate. She has become the head of a minor branch family in the Audenrieth dukedom. At first, she is living peacefully, cared for by her family's servants, but then she is suddenly attacked! A battle for Audenrieth succession has begun, and she can either fight or surrender her inheritance.

After the attack, Marina is left only with her butler Sydow, a strange fighting machine called Eunos, which was activated by the keywords her father gave her on his deathbed, and her family's special draupnir gun. To win the competition, Marina must take the draupnir guns of the other families. Marina decides that she will take part in this dangerous competition, but will a 10-year-old girl be tough enough to really stand a chance?