isn't this the sequel of Dark Sphere?
Well, there is no denying that:
- Knight Slave is another (in order) game from this author;
- The main character looks very similar, except that she differs quite a lot in her body shape (which, however, can be explained, for example, by the fact that then she was very young and now she is "mature")
- Her name in Dark Sphere was translated as
Riffie, while in Knight Slave as
Refia (but this may be due to the difference of the person who translated the game).
However, it is probably not an official sequel. The similarities may be due to the taste of the author(s).