Abandoned by his parents and spurned by all others, Allen Walker found solace in Mana, his adoptive father. As cruel fate is, he died, and in a desperate attempt to see him again, Allen made a pact with the devil- and ended up being cursed by his father.

But the curse- of being able to see the misery of his hated enemies, the demons, started Allen's journey. He learnt he was an exorcist, destined to fight God's war with his unique power.

That power, and a promise to always keep walking, is what makes the Destroyer of Time go on.