Kazusa is the second eldest of the Sugimoto sisters.

She is a gentle woman who people gravitate to because of her sweet nature and affability, though as Yasuko notes, she is a very rough and grounded person. She knows that both her sisters loved her boyfriend. She jokingly though piercingly and truthfully says that she took Kagami for her own and would never give him up to either one of them.

Out of all the sisters, she seems to be the least eccentric and blunt though unlike the rest of them, when she does speak her mind, her words are harsh and borderline cruel because of her honesty.

She once was a colleague of Yamashina Hinako and Kagami, as she was an art teacher in Fujugaya.