Read Miracle Hero! Manga
This is the tale of a ‘Holy Warrior’ who sealed the Demon Lord with his divine powers and holy sword.
However, the protagonist is in truth some lame guy who happens to run out of luck often, and the sealing of the Demon Lord was no exception.
Now our unfortunate hero and his two trusty (and much cooler) companions must get him out of the deep shit he put himself in.