Seiya Mashiro♀

Mashiro is Shinya’s neighbor, childhood friend and best friend. She is a pretty normal girl with hidden feelings for Shinya, making her a bit of an underdog. But in spite of overwhelming obstacles and her own lack of self-confidence, she tries her best whether in the pursuit of love or fulfilling the duties of being a “good” Santa. Despite the fact that she was born into a family following the Christmas tradition, she acquired a fear of heights which makes her completely helpless when riding a flying sleigh.

[From m3rryweather's review]