The keeping of pillow books to record poems, secrets, and encounters with lovers was a common practice of noble women in Heian Japan. Although its content is unrelated to the film, a famous example was written by Sei Shonagon at about the same time as Lady Murasaki's The Tale of Genji which has the honor of being the world's first novel. In fact, it has been said that Sei Shonogon and Lady Murasaki were rivals in the court of Heian.
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