Ki no Shizuko (紀静子)

KI no Shizuko (year of birth unknown - February 866) was Emperor Montoku's koi (a lady waiting in the court or court lady). Daughter of Shoshiinoge (Senior Fourth Rank) Hyoefu (Headquarters of the Middle Palace Guards) KI no Natora. Little sister of KI no Aritasune and KI no Taneko (Emperor Ninmyo's koi).
She was called Sanjo no Machi

She became Emperor Montoku's Koi, and became the mother of Imperial Prince Koretaka, Imperial Prince Koreeda, Imperial Princess Tenshi, Imperial Princess Jutsushi, and Imperial Princess Chinshi. Imperial Prince Koretaka was expected by his father, the then emperor, but he could not be Imperil Crown Prince, because Shizuko was from the Ki clan and had no backing. She was conferred Shogoinoge (Senior Fifth Rank, Lower Grade) in January 858, and later she was raised to Jushiinojo (Junior Fourth Rank, Higher Grade). She died in February 866.

One piece of her poetry was included in "Kokin Wakashu" (A Collection of Ancient and Modern Japanese Poetry (poem number: 930)).