Sefiros Eishi: Chased By Flame

Mykel LeKym is a crippled librarian, stuck in a medieval-era kingdom where strength is valued over intelligence.
While other boys learn swordplay, Mykel is in his home’s library, learning and reading. When he finally comes of age,
he is given over to his godfather Lazarus as an apprentice. One day they are on route to the capital to deliver books when everything changes.

The demonic entity Sutyr. John Jekai, a mage-slayer with an unknown grudge against Mykel. Lazarus himself, guardian to eldritch knowledge. These men converge on an unholy vigil for one purpose: The mystical weapon Ifirit. Sutyr wants it, but Mykel bonds to it first, and in doing so activates a secret so deeply buried that its existence has faded to myth. Thus a crippled librarian’s world is turned on its head . . . and the fate of existence itself hangs in the balance.