The POV was on the sacrificed girl's, if that helps.
Basically, the girl goes up a mountain or into the woods, I forgot, and she finds the demon monster. She thought it's her end, but the demon monster was actually chill.
Turns out he was isekaid and got here. He found another demon monster like him but it was aggressive so he killed it. And now he's alone.
Girl keeps him company, guy's demon biology makes him horny, girl jerks him off, not enough so they have sex.
The monster was referred to as a demon/devil if my memory serves me right.