Aoi Otoha/Rythm Broché from Henshin Heroine ga Aku ni Ochita Hi, a manga series by Group Gohan Oomori.
The chapter 2 translation calls her Note Brooch, but once again I'm sticking with the chapter 1 translation for this.
Description
Rythm Broché - rythmnotebroche, magical girl, 1girl, solo, blue hair, short hair, light blue eyes, hair ornament, choker, elbow gloves, strapless shirt, neck ribbon, brooch, dark blue overskirt, blue skirt, back ribbon, dark blue thighhighs, blue boots, high heels,
Aoi Otoha - aoiotoha, 1girl, solo, medium hair, blue hair, dark blue eyes, hairband, white shirt, collared shirt, short sleeves, red bowtie, dark blue cardigan vest, dark blue pleated skirt, black kneehighs, brown loafers