Supreme Magus in another world

The monster horde that emerged from the gate 18 years ago came from all directions in space and time. Concurrently, humanity began to realize their own potential and hunt monsters for glory and fortune. Needing money to take care of his sick mother, Caesar takes a risky profession helping to hunt those monsters by serving as bait for the hunters. After being severely hurt by a monster, though, he recalls his prior life as a Supreme Magus from another world.