I know this probably won't matter to many of you. I was just thinking about this game and how fun it was. You are one of two Assassins, Ayame or Rikimaru and you follow their paths throughout the game. The story of what Rikimaru had gone through while he was absent is explained and you even get to play that part of his life. All the while, you are trying to keep the antagonist from bring back the lord of hell. Not a lot of romance, but it was one of my favorite games.
It is for Xbox and the first version of it isPS2, so it may be all but extinct. But I highly recommend that you find and play some others in the series, such as Birth of the Assassins, or Stealth Assassins. It's a really fun game and worth playing if you can find it.