Kokugensou wo Item Cheat de Ikinuku THE COMIC

A timid and unremarkable high school student finds himself in a harsh fantasy world, lacking skill in swordsmanship or magic despite his desire to become a hero. Relying on knowledge gained from modern Japan, he seeks to turn it into a means of survival by converting it into money. Through this process, he takes on various roles, including a secretary assistant, owner of a trading company employing slave girls, a knight, and eventually a hero.