Isekai Cheat Magician

The Golden Swordsman Myura leads Taichi and Rin to the mage, Lemiya. After a reevaluation they discover that both of them possess astounding magic power, and so they begin to train under Lemiya's tutelage. During their training Rin begins to get a feel for how to cast magic. On the other hand, Taichi faces difficulty using his magic power, but just as he's about to give up on mastering his task in one day he hears a mysterious voice.