>>532681686
tldr the villainess turns out to have been a victim and the protagonist had a hand in it in her past that he no longer remembers
it's the classic tragedy of a former friendship/love interest becoming your enemy, and she dies (at your hand no less) without you getting the chance to make amends for the past

every story worth telling has something to tell us about our lives, and this one hits a core anxiety: leaving things unsaid or undone and death coming randomly and meaninglessly robbing you of the chance