The Captain of an elite knight order, Yuu Brown (25-years old), realizes the limits of his capabilities and left the order to become an adventurer. Meanwhile, dropout from a famed magic academy, Tifa Vega (8-years old), felt her life choices being closed off one after another. She held an abnormal amount of mana, but was terrible at magic. The two were never supposed to cross paths, but Yuu came to know of the girl’s circumstances, and decided to train her himself. However, his training style was that of the unorthodox style he had used in the knight order—. What will the combination of the spartan trainer and failure result in!?