The Fang Oath: RebornEpisode 9

Reborn on the day of the Mating Ceremony, I placed my wolf-fang necklace around my sister's neck and let her marry the Alpha's heir—the man who was meant to be mine. I thought this would save everyone. Until he stood before me, eyes red, and said, "There was never a Clara. From beginning to end… it was only you."