onozukai no ossan bōkensha ichaerohāremu eiyū tan (Associated Names)

Douglas is an adventurer who uses an axe as a weapon, a very serious and hard-working man who has lived an unrewarding life. One day he is betrayed by his teammates in the depths of a dungeon, and almost loses his life. In the midst of his despair, he finds an axe, a fearsome weapon…