Mizusawa Chizuru

She is the older sister of the main character, who is an office worker. She is a “kind and caring older sister,” but on the outside she is a serious and capable office worker.

She has a rigid image of herself, partly due to her strict nature, and she is not popular with the men. She had a boyfriend and experienced young girlish things, but after she started working, she became estranged with him.

She has a body that has known the joys of being a woman, but now she's pent up and spends her days secretly comforting herself without her brother hearing it.