The shadow of vessel

So imagine a world where demons completely rule everything.  Theyve been wiping out whole cities just eating humans, and they divided the territories among themselves.  Because of all the demon attacks, the human population dropped to literally 0.5%.  So all the demons made a pact with each other. Now, they only sacrifice one human every day. Our main guy (the vessel) is super poor.  He owes a ton of debt, so society basically just tosses him out and sends him to be the sacrifice for the demons.  But the demon hes given to is actually on the verge of death. Instead of eating him, it makes a contract with him.  This gives our guy this crazy shadow power where he can turn anyone whos dead into a part of his own shadow army. Now he actually has a chance to save humanity and kill all the Demon Kings.  But theres a massive problem... the demon basically has control over his body. The big question is, will his childhood love be able to pull him out of the demons control? And will he really be able to wipe out all the demons in the end.