The way to resist to Zanki could be used to resist even to Soul Edge's mind control. If that is, then Setsuka could become one of the few that could resist to Soul Edge...
True, but the story isn't just Setsuka's story. Mitsurugi's Side Story took part of the story too, but at least we got to see what happened in regards to Setsuka's background.
You mean the intro where she says they’re the same? She actually says this to a few characters, those who have some desire for revenge on someone else, like herself. She can sense Maxi’s thirst for revenge against Astaroth, Nightmare/Siegfried’s desire for vengeance for his father, stuff like that. She also has a special intro for the younger characters like Amy and Talim.