I don't think Kashiwa's girlfriend is being totally cissexist and not understanding. I got the idea that she loves Kashiwa and wants to marry her and have kids with her but realizes the difficulty of two women being together in Japan. She wouldn't be able to marry her or adopt kids with her if Kashiwa was legally female. Maybe she could stay living as a woman but keep her papers male, but it seems like she's too dysphoric.