Lady Murasaki, niece of Fujitsubo, bears such a striking resemblance to her aunt that she captures Genji's attention at approximately ten years old. Orphaned of her mother, she resides under the care of her grandmother—a nun—and her nurse, Shōnagon. Compelled by her likeness to Fujitsubo, Genji spirits Murasaki away to his palace despite resistance from her guardians. He assumes her upbringing, personally instructing her in writing, music, and courtly arts to shape her into his ideal companion.

Initially wary after her abduction, Murasaki gradually develops trust in Genji, viewing him as a paternal figure. This trust fractures when, following his wife Lady Aoi's death, Genji initiates a sexual relationship against her will. The narrative depicts her profound sense of betrayal and confusion, as she never anticipated this shift. Despite these feelings, Murasaki acknowledges her dependence on Genji for status and security, leading her to maintain affection while suppressing distress. She becomes Genji's primary companion and de facto wife, though her lack of influential family prevents formal marriage.

Throughout their relationship, Murasaki exhibits persistent jealousy, particularly toward Genji's other romantic interests. This intensifies regarding the Akashi Lady; their daughter becomes a source of pain for Murasaki, compounded by her own childlessness. Her jealousy further strains their bond following Genji's political marriage to the Third Princess (Nyōsan). Even after Genji's political ascent and the construction of Rokujō-in to house his significant relationships, Murasaki remains his favored companion.

In later years, Murasaki suffers prolonged illness and seeks permission to become a nun—a wish Genji refuses. Her health declines steadily, culminating in her death, which precedes Genji's own demise. Her passing deeply affects Genji, prompting his contemplation on life's transience.