The Blood of Awakening, the Priced Life

Magical energy comes from the "origin of life". The human race is born with a meager but reproducible source, which grows slowly through exercise and reproduction; the demon race is a powerful "condensation of life source", but it is almost impossible to recover naturally, and consumption means permanent dissipation and death. Therefore, the demons must "obtain" the origin through specific methods in order to maintain their existence. The protagonist Eli Green is a human being who accidentally possesses "infinitely renewable origin", and he has therefore become the "Holy Grail" coveted by all forces.