The world is a fantasy like RPG where half of human population is an adventurer to protect the kingdom away from the tragedy that happens 200 years ago. Doan Rai Tsukio examined himself and he was bestowed an unknown class. He becomes an adventurer for the sake of his younger sister with a curse of agony, just him alone took the responsibility of saving her from the curse. He works really hard to survive and find a solution for her sister's curse.