As a novel overwhelmingly concerned with Genji's numerous romantic pursuits, the relationship between men and women and the respective role that each sex is supposed to play in Heian court culture is extremely important. Specifically, The Tale of Genji illustrates how women are disadvantaged and disempowered by the laws and customs of the world they live in, while also suggesting that by either subverting those customs or very carefully cultivating the affections of powerful men, women can find a modicum of control over their own lives.
Throughout most of the first half of the novel, women are shown in most cases to be at the mercy of the whims and desires of the men around them. This is especially true when it comes to sex and sexual relationships—and in particular, the ways in which it's considered appropriate for men and women to interact with each other. All of the women in Genji are expected to keep themselves hidden from men other than their fathers and husbands. They do this by conducting their lives from behind screens or curtains and communicating with men primarily via written poetry passed back and forth with the help of messengers.
Despite the existence of the screens, however, women were actually not afforded much privacy and the screens did little to protect them from men's gazes. Men, especially Genji, consistently peek behind screens to catch glimpses of women they're attracted to, and the screens provide hidden places in which men can begin sexual relationships with women, often initiated through rape. Further, because the women are supposed to be hidden and often bear the blame for men’s actions, the women that Genji forces to have sex with him often feel unable to call for help—doing so would damage Genji's reputation as well as their own, making giving into Genji's demands the lesser of the two evils. This overwhelmingly suggests that women live their lives constantly vulnerable to the often-unwanted advances of the men around them and are equally unable to escape the ensuing sexual relationships for fear of retaliation.
As distasteful and forceful as many of these relationships' beginnings are, the novel does suggest that having sexual relationships with the right men (regardless of the details of the relationship's origins) is actually a very effective way for women to become extremely powerful. This holds true in particular for Kokiden, the Emperor's wife. Through their sexual relationship, Kokiden is able to navigate herself into a position of immense power when her son with the Emperor, Suzaku, becomes emperor himself. So influential is Kokiden that she becomes largely for sending Genji into exile. The same thing plays out later in the case of Fujitsubo (one of the Emperor’s favorite lovers) and her son, Reizei. Though Reizei is actually Genji's biological child, Fujitsubo and Genji keep this information secret from the Emperor. Because of this, Fujitsubo is able to maintain her powerful position and catapult her son to the emperorship at a very early age. This illustrates how a woman's sexual past can actually protect her from what would otherwise have the power to irreparably damage her reputation, assuming she can keep specific damning information (such as Reikei's paternity) out of the rumor mill.
In the case of the Akashi Lady, a young woman of humble (that is, country) birth, her sexual relationship with Genji is similarly implied to have the power to elevate her to the status of a court lady. After she gives birth to Genji's only daughter, who was foretold to one day be empress, Genji promises to bring her and the baby to court. This is a previously unheard-of promise and one that would solidify the Akashi Lady's standing as someone important and reasonably powerful, despite the disadvantage of being born and raised outside the city.
Of course, Genji never follows through with his promise in the novel, underscoring that even as women obtain power, they're still dependent on their relationships with men to gain and then hold onto that power. This suggests that even as women do ascend to these powerful places in Heian society, they're only able to do by working within a system inherently stacked against them and by using the abuses they suffer to their advantages whenever possible.
However tenuous this power may have been at the time, it's also worth noting that in the long run, the Heian women ultimately came out on top: Murasaki Shikibu herself worked within the system she describes, and her work and that of other female writers has far outlasted and been significantly more influential than any literary works by their male contemporaries.
Women, Sex, and Power ThemeTracker
Women, Sex, and Power Quotes in The Tale of Genji
In a certain reign there was a lady not of the first rank whom the emperor loved more than any of the others. The grand ladies with high ambitions thought her a presumptuous upstart, and lesser ladies were still more resentful.
Because she was of such high birth (it may have been that people were imagining things) she seemed even more graceful and delicate than the other. No one could despise her for her inferior rank, and the emperor need not feel shy about showing his love for her.
She was of an extraordinarily gentle and quiet nature. Though there was a certain vagueness about her, and indeed an almost childlike quality, it was clear that she knew something about men. She did not appear to be of very good family. What was there about her, he asked himself over and over again, that so drew him to her?
The weak ones do have a power over us. The clear, forceful ones I can do without. I am weak and indecisive by nature myself, and a woman who is quiet and withdrawn and follows the wishes of a man even to the point of letting herself be used has much the greater appeal. A man can shape and mold her as he wishes, and becomes fonder of her all the while.
"It would be nice, I sometimes think, if you could be a little more wifely. I have been very ill, and I am hurt, but not really surprised, that you have not inquired after my health."
"Like the pain, perhaps, of awaiting a visitor who does not come?"
She did not seek to hide her distress, and her efforts to turn him away delighted him even as they put him to shame. There was no one else quite like her. In that fact was his undoing: he would be less a prey to longing if he could find in her even a trace of the ordinary.
The hand was very immature indeed, and yet it had strength, and character. It was very much like her grandmother's. A touch of the modern and it would not be at all unacceptable.
Murasaki was the perfect companion, a toy for him to play with. He could not have been so free and uninhibited with a daughter of his own. There are restraints upon paternal intimacy.
Fujitsubo was tormented by feelings of guilt and apprehension. Surely everyone who saw the child would guess the awful truth and damn her for it. People were always happy to seek out the smallest and most trivial of misdeeds.
Naishi, though much discommoded, did not protest with great vehemence. There are those who do not dislike wrong rumors if they are about the right men.
In the Seventh Month, Fujitsubo was made empress [...] Making plans for his abdication, the emperor wanted to name Fujitsubo's son crown prince. The child had no strong backing, however [...] The emperor therefore wanted Fujitsubo in an unassailable position from which to promote her son's career.
"It will do you no good. I am always allowed my way. Just be quiet, if you will, please." [...] Though of course upset, she evidently did not wish him to think her wanting in good manners.
Genji felt like a child thief. The role amused him and the affection he now felt for the girl seemed to reduce his earlier affection to the tiniest mote. A man's heart is a very strange amalgam indeed!
Though avoiding display, he took great pains with her initiation ceremonies. She found the solicitude, though remarkable, very distasteful. She had trusted him, she had quite entwined herself about him. It had been inexcusably careless of her.
Memories had dimmed over the years, but now the astonishing resemblance did a little dispel his gloom. The dignity that quite put one to shame also reminded him of Murasaki. He could hardly think of them as two persons, and yet, perhaps because Fujitsubo had been so much in his thoughts over the years, there did after all seem to be a difference.
They lived precarious lives, completely dependent on Genji. So lonely indeed was their mansion that he could imagine the desolation awaiting it once he himself was gone...
He thought that he could hardly be expected to visit her. She had her own ideas. She knew that rustic maidens should come running at a word from a city gentleman who happened to be briefly in the vicinity. No, she did not belong to his world, and she would only be inviting grief if she pretended that she did.
Though she saw little of him, the lady was completely dependent on him; but she was not of the modern sort, given to outpourings of resentment. He knew that she would not make him uncomfortable. Long neglected, her house now wore a weirdly ruinous aspect.
Her soft voice, trailing off into silence, was very pleasing. He sighed, almost wishing it were not the case that each of his ladies had something to recommend her. It made for a most complicated life.