If you're looking for manga similar to Fate/Prototype: Sougin no Fragments (Light Novel), you might like these titles.
In order to save his life, Tooya made a pact with the ancient demon. The price is he has to pick a person for it to eat every month
Nothing could have thrilled Kimihiro more than stumbling upon the bizarre wish-granting shop of the beautiful but unnerving Yûko Ichihara, who solemnly promises to make the spirits plaguing Kimihiro go away just as soon as her fee–rendered in daily afternoon chores at her shop–is paid in full. Of course, the thrill wears off as soon as Kimihiro realizes that his payment plan bears a disturbing resemblance to indentured servitude . . . eternal indentured servitude. Still he soldiers on, ready for whatever number of adventures lie ahead. But in Kimihiro’s case, three may not be the charm!
A battle has broken out among rival sorcerers. The most nefarious group, the Necromancers, is killing young girls in Hong Kong to read the future in their entrails. Carno, a human youth raised by Aeromancers in a different dimension, is summoned back to his homeworld to join in the battle. Does Carno have what it takes to survive in a world of political alliances and emotional entanglements?
Magicians, people with magical powers that have caused their kind to be hated and feared throughout the centuries. Tales of magic for both good and evil, the struggle to fit into society, and a dark past that haunts them both.