Homura "Haruka and Kanata are free of you... I say so. ALL of their friends say so. Believe me when I tell you, if I EVER SEE or HEAR you try to so much as lay your filthy finger on either one of them... I will find you, and I'm sure as hell the next time we met, YOU WOULDN'T BE THIS LUCKY."
Happened during Homura's time in Shibata. After hearing about what the Saigusa family did to both Futaki and Haruka, Homura disguises herself as "Mask The Saito" and pay a 'little visit' to the family. She destroys the entire Saigusa household and killed or injures several members, leaving the head of the Saigusa family, Mr. Saigusa, the man who made the twins' life a living hell, at the mercy of her feet. For the final warning, Homura threatens the old man to never lay his hands on Futaki and Haruka ever again. And then, she leaves the terrified old man at what's left of his family's household.
And yes...Homura took the role of Mask The Saito instead of Kyosuke.
Homura Akemi from Puella Magi