Kokuu is a lady-in-waiting in the Jade Pavilion, the residence of Consort Gyokuyou within the imperial palace in the anime The Apothecary Diaries. She is a minor character who serves alongside her older sister Hakuu and her younger sister Sekiu. The three sisters entered Gyokuyou's service prior to the birth of the Crown Prince, which suggests an established history and trust within the consort's household. Kokuu's role is primarily domestic, involving tasks such as cleaning, cooking, and general upkeep of the pavilion. As a working member of the palace staff, she forms part of the background court life and interacts with other ladies-in-waiting, including Maomao. The narrative does not explore her individual personality in depth, but she is portrayed as a dutiful and unassuming servant. Kokuu does not undergo significant personal development or play a direct role in the major intrigues of the story; instead, she contributes to the rich depiction of the court's inner workings and the collective of servants who support it.