運送屋のおっさんがなぜか副業で絶対無敵剣士を務めることに～さえない人生を送ってた俺が魔王討伐の切り札に？～

The manga centers on Jack, a middle-aged freight company employee, who suddenly becomes the key to defeating the demon king, when he is told that he is blessed with the strength of a legendary swordsman. He then decides to become an invincible swordsman as a side job. (Source: Anime News Network)