Soul Reaper by Eve Langlais

Being a hero would be a lot easier with an instruction manual.

A hero’s work is never done! I’m the guild’s only reaper witch and it’s my job to save humanity. After a few hiccups, I rose to the challenge and expelled the demon king from Earth, however, Moloch’s time in exile allowed another demon prince to rise in ranks. Not good since this self-proclaimed Emperor of Inferis is planning an invasion.
While I’ve managed to finally hone my magic and no longer suck at physical combat, there’s still much to do. Seducing two sexy reapers is at the top of that list, but I also need to pay a debt to a mysterious voice.
Finding a body for the portal entity to inhabit might have to take a backburner, though, given everything else going on. The new demonic Emperor isn’t just looking to rule Earth, it’s got an interest in me, I just can’t figure out why. Perhaps it’s time to put down the training scythe, hit the books, and learn the origin of my power.

The truth ends up being even worse than expected and I might have to do the unthinkable to save everyone I love. I only hope I don’t lose my soul in the process.