It narrated a story of a 15-year-old girl who found a legendary neck corset in a mysterious box that fell upon her from above. All of a sudden, the corset jumps out of her hands, wraps around her neck and turns her into "Headbangya!".
It's actually a symbol of her going to a rock/metal concert for the first time. The neck corset is there to "train her neck" as she starts to headbang to the metal concert as a first timer. She is dressed normally as she starts to headbang but at the end of the video, you can see she's wearing the costume, indicating end of the performance as she drops on her bed, tired after her first concert and headbanging.