I am asking this because I could not find a related post anywhere. From what I infer from the source material, Sensei is a woman who is unusual for her age and gender. Not only does she have childish tastes, she is tomboyish. Even when acting like an adult, she resembles an old man, in Hikki's words. Hikki himself wonders about it when hanging out with her, esp. when driven by her in her aston martin. She also had several failed marriage interviews from what I read in Volume 5 and seems to attract "hobos" who took away her furniture.
Is her tomboyish/masculine nature the reason for putting off potential suitors? Does her nature also clash with the expectations of femininity in Japanese culture?