While I find the idea of eternal vindictiveness tiring, especially for someone who isn't even real, I find myself agreeing with people who say they can't trust Kaoru. One extremely necessary part of a redemption story is the breakdown of the character to be redeemed. The breakdown moment, where they're at their lowest and realize the way they do things isn't right, is essential for convincing the reader that they've actually learned something. This series has been going on for so long, with such time between chapters, I honestly can't remember if Kaoru even had such a moment. If she did, and people just aren't recalling it, please feel free to link the chapter.