How to Save the World — Tam MacNeil

Sean and Alex, hired killers in a world infested with death gods, are ready for a career change. Sean gets what he wanted, but his partner in crime and lover, Alex, isn't so lucky. While Sean gets to start a new life, Alex winds up pilotting the mech that is humanity's last great hope against the shinigami. The trouble is, it's real hard to kill a death god. And those mechs? Turns out they eat humans, and spit out machines.