FFF Geum Gwansimyongsa

A boy named Han-Soo Kang is suddenly transported to Fantasia, a fantasy world ruled by demons. He is hailed as the Chosen Hero and spends ten years training to defeat the ruler of Fantasia. However, he finds the task unexpectedly easy and looks forward to returning to his original world. Just then, the "god" of Fantasia steps in, presenting a report card that reveals heroism involves more than just strength.