Pansy Parkinson – “The Vow He Never Meant to Keep”
Fifth year, drunk on firewhisky and grief after his mother’s anniversary, Arlo makes a mocking Unbreakable Vow with Pansy in the Slytherin common room: “I will never fall in love with anyone at this school.”
Years later, the magic starts killing him slowly every time his heart races around her. He hides the pain. She notices anyway. The only way to break the vow is for one of them to mean it when they say “I love you” out loud. They spend an entire year dancing around those three words while he literally bleeds for her in silence.