I have not made a comment on this site before, but feel compelled to in light of the comments above.
Whilst I like the idea of a sequel, I am happy with the story as it currently stands - including the twist where Edwin chooses to become an angel rather than a demon. A fairytale ending would be inconsistent with the rest of the story and does not reflect real life. Also, I prefer it when authors allow readers to come up with their own thoughts as to what happens next. Having everything neatly 'tied up' and presented to the reader in full detail feels false to me as again it does not match real life where there are multiple intersecting and overlapping stories that do not come to an end at the same time.
Considering the dangers involved in the story, the 'body count' is actually quite low. There are so many triumphs that the ending could be seen as too positive:
Edwin loved his sister enough that he was willing to give up potential happiness for hers (I say potential as there are no guarantees) - and Lothar loved Edwin enough to let him go.
Ida is rescued and leads a new life in celebration of Edwin's sacrifice and without the influence of her father
Isolde appears to have also been able to move forward with her life and less controlled by her past
Similarly, Reiff now knows what happened with Helga, and through this closure is also able to move on with his life
There is justice for Ida, Helga and Mildburg
I also see potential problems with Lothar and Edwin just getting back together again. Whilst Edwin voluntarily chose to be an angel, it is likely that over time, he would end up like Helga - i.e. fundamentally changed and no longer the same person. It is plausible that the same could occur if he had chosen to become a demon instead. Also, it would be only because of his love for Lothar that Edwin would consider such a choice, as to me, becoming a demon would be incompatible with Edwin's nature.
