I played the VN hence my disdain when I found out Bee Train (no thanks to their inept Blade of the Immortal series) is animating this series. Since I knew the story will be based on Ein/Elen's ending, I did not watch the series until the conclusion where there is little twist in the end, Reiji was shot by INFERNO assassin in the back while he is watching Elen admiring the skies of Mongolia like the ending of the route. I was pleasantly surprised by it, the ending fits the theme of the story, IMHO.
Cal story is she "born" with tainted hands of Reiji and by his hand she will "return" to him. Despite his grief, Reiji conscience is somewhat eased with knowledge that Cal will not go on killing and lived his erstwhile empty life during his time in Inferno. Her death is not in vain, she is free from path of no return and served as closure to Reiji's deep anguish as much as her's.
The theme of this story always revolves around there is always a consequence for any path despite who you are, Cal and anime unique Reiji's tragic last exit meant to show this.
Reiji succeed in saving Elen so his "debt" to her is done. But he can't escape his past so the last bullet is his absolution for his other horrible deeds. He is free but at the cost of his life.
After all, there is no more purpose of living for Cal and Reiji, to be honest. In VN where Cal is the focus, they both still living the path of blood in the end, becoming a modern version of Bonnie and Clyde which I don't consider as quality living.
However, I must add, the anime ending is bit ambigious; some people think Reiji is wounded whereas I think he is dead. Different strokes for different folks.
The ED song is lovely, KOKIA gave a sorrowful and fitting end to the story by her sad lullaby.
