Hmm... 3 1/2
The ending is not satisfying.

Spoiler

He chooses her over trying anymore to save his brother. That will be left to the other immortals. And it is not made clear how their life will go with her mortality and his immortality.

add to that a bit of sex that just didn't do it because two more entities were involved. Not being a prude but it just wasn't sexy for me. This is a bit on the graphic side also but I was expecting that. A definite PNR but with a good back ground story that I thought maybe could have ended when

Spoiler

She comes to save him at her house. He has decided his brother is lost and picks her over him. Then she invokes all the witches and the power is overwhelming for the demon, yet... he doesn't attack the demon before he/she escapes and then lets the demon grab his crazy brother too and take him.

it was not a good conclusion but neither was the final conclusion either

Spoiler

He quits pretty much because she is killed. He takes her to the goddess rather than defeating the all powerful demon and the warped minded brother.

So it was a good story but had serious issues. I give it a 3 1/2 and want to bump it up but not really. So on the fence.