Elevator pitch for Gray Familiar:
Large cast of human/monster partnerships.
A thing I always thought about stuff like those kinds of shows was that humans are a bit useless in fights scenes. So I gave the humans powers in Gray Familiar. But those powers kinda suck, because the typical human body is too frail to use them without entering a coma.
And that's how I came up with the ingenious (TM, OC don't steal) idea of basing the human/otherworldly being partnership on a pact beneficiary for both. Humans can use their abilities, and the monsters are fed by the excess energy released by during the process.