Sister Lover was a Japanese manga about the love story between the protagonist and his half-sister. The ending of the manga had not been decided yet because the storyline had not yet ended. Some readers and the media speculated that the manga might usher in a happy ending where the protagonist and his half-sister could find their own happiness. However, these speculations were just speculations. The details of the ending of the manga would only be known after the work was completed.
Grave Robber's Chronicles is a famous novel and manga. I've read both of them. Personally, I prefer novels.
The plot in the novel was more vivid, the characters were more distinct, and the plot had more ups and downs, allowing the readers to feel the emotions and psychological state of the characters in the story more deeply. In addition, the ending of the novel version was more satisfying. After all, the ending of the novel was what the readers really wanted to see.
Of course, the comic version of Grave Robber's Chronicles was also very popular. It made the plot of the novel more vivid and interesting through the form of comics. However, if you prefer the novel version of the story and character, then the comic version may not be suitable for you.
Well, it seems the warrior had some sort of conflict with the hero and his lover. Maybe he knew a secret that could expose them, and that's why they got rid of him.