When Emperor Uda ascended to Japan’s Imperial throne in 887 at just 21 years old, he became the country’s 59th ruler—but his most enduring legacy may be the personal diary he kept throughout his decade-long reign. Known as the Imperial Diary of Emperor Uda, it is the oldest surviving diary from the Japanese court. It offers an extraordinary window into the Heian period, a time that deeply shaped Japan’s culture and politics, recording everything from state affairs to intimate daily moments. Uda was not only a reform-minded monarch who worked to raise ethical standards among his officials, but also a man with a deep fascination for Yin Yang divination, astrology, and the study of omens.
His diary reveals how these spiritual practices guided his decisions and beliefs. One particularly notable entry, dated March 11, 889, stands out for an unexpected reason: it is the first recorded mention of a domestic cat in Japan. In poetic and affectionate detail, Uda described a black cat originally given to his father, Emperor Koko, by a returning governor. The emperor compared his cat to a crow for its dark fur, noted that it measured about a foot and a half in length, and wrote that when curled up it looked like a black millet berry.
He praised its hunting skill, describing it as better at catching mice than all other cats. “My cat moves silently, making not a single sound, like a black dragon above the clouds,” Uda wrote. He also described the cat’s bright, needle-like pupils and ears that stood straight up like the bowl of a spoon. The emperor fed the cat milk gruel every morning and cared for it for five years.
He explained that his devotion went beyond admiration for the animal’s talents, noting that the cat had been gifted by his father, the former emperor. Uda even addressed the cat directly, saying it possessed the forces of Yin and Yang and suspecting that the animal might understand him. In the diary, he wrote that the cat sighed, raised its head, and stared at his face, seeming too moved to reply. For the emperor, the cat was more than a companion—it was a living embodiment of nature’s balance, representing the harmonious equilibrium of opposing forces central to the philosophy of his time.
The entry blends playful affection with philosophical reflection, offering a rare glimpse into Uda’s private world. Unlike later emperors who became symbolic figureheads during the age of the samurai, Uda still wielded genuine political power, and his diary captures a ruler with real authority. Historians consider these court diaries among the most valuable resources for understanding pre-modern Japan. While very few have been translated, they provide intimate portraits of influential figures and the complex relationships that defined the Imperial court.
Through Uda’s writing, readers see an emperor not only as a political leader but as a man with passions and connections reaching far beyond court intrigue—a man whose thoughts ranged from celestial matters to his cherished pet. His account of the black cat remains a charming and historically significant moment: proof of a domestic cat in ninth-century Japan, recorded by an emperor who saw in his pet a reflection of the cosmic balance that governed his world.