After saving the world, the strongest hero who has no place to go anywhere · Leo. Power that is too strong can not enter the peaceful world …… Such a place of employment where he arrived – the former enemy, the Magus army! The 2nd Kakuyomukon.

From Shoujo Crusade:

One day, Hirazono Satsuki, while walking home from work, finds a girl in a garbage dump. He ends up taking her home and she introduces herself as Riene, an exorcist. She is on a quest to find somebody who took care of her before, a girl named Satsuki. Could he be the same Satsuki?