Oichi (お市, Oichi?) (sometimes spelled O-Ichi, 1547 - 1583) lived during the Sengoku Period of Japanese history. She was the sister-in-law of Nōhime and the younger sister of Oda Nobunaga. Oichi was renowned for her beauty. She was descended from the Taira Clan and Fujiwara Clan.
Following Nobunaga's conquest of Mino in 1567, in an effort to cement an alliance between Nobunaga and rival warlord Azai Nagamasa, Nobunaga arranged for Oichi, then twenty years old, to marry Nagamasa. This was unusually late for a first-time marriage, fueling speculation that she may have been married earlier.
Oichi had four children with Nagamasa, a son, Manjumaru, and three daughters, Cha-Cha, O-Hatsu and O-go. But in 1570, Nobunaga attempted to conquer the Asakura clan, a traditional ally of the Azai. Nagamasa broke his alliance with Nobunaga and sided with the Asakura clan. A story relates that she sent her brother a sack of beans tied at both ends, ostensibly as a good-luck charm but in reality warning that he was about to be attacked from both front and rear by the Asakura and Azai clans. According to the story, Nobunaga got the hint and retreated just in time.
Fierce fighting broke out and continued for three years until the Asakura family and other anti-Oda forces were killed off. Oichi remained with her husband at Odani Castle throughout, even after Toyotomi Hideyoshi, a trusted vassal of Nobunaga at the time, began laying siege to the castle. Eventually Nagamasa was surrounded at Odani, but before the final attack on his castle commenced, Nobunaga called for the return of his sister. Nagamasa agreed and sent Oichi away with their three daughters. Nagamasa and his son, Manjumaru, remained walking into the fire and honorably committing suicide after he admitted to Oichi how he loved her.
Oichi and her daughters remained in the Oda family's care for the next decade. After Nobunaga was assassinated In 1582, his sons and vassals broke into two major factions, led by two of Nobunaga's favorite generals, Shibata Katsuie and Hideyoshi. Nobunaga's third son, Nobutaka, belonged to the former group, and arranged for his aunt Oichi to marry Katsuie in order to ensure his loyalty to the Oda clan. But in 1583, Katsuie was defeated by Hideyoshi in the Battle of Shizugatake, forcing him to retreat to his home castle at Kita-no-shō. As Hideyoshi's army lay siege to the castle, Katsuie implored Oichi to leave the castle with her daughters and seek Hideyoshi's protection again, but this time Oichi refused, insisting on dying with her husband, although she did send her daughters away. They sat there when the castle was in flames.
Oichi's three daughters each went on to become important historical figures in their own right. The eldest and the most famous, Cha-Cha became a concubine to Hideyoshi--an irony, considering Hideyoshi was directly responsible for killing not only both her birth parents but also her stepfather. She became known as Yodo-Dono or Yodo-Gimi (from Yodo Castle, given to her by Hideyoshi), and she bore him his only two sons, including his heir Hideyori. Yodo-Dono and Hideyori later died at the hands of Tokugawa Ieyasu in the Siege of Osaka, the final battle of the Warring States era.
The second, O-Hatsu, married Kyogoku Takatsugu, a man from a noble family once served by the Azai clan. The Kyogoku clan sided with Ieyasu after Hideyoshi's death, giving her the means to serve as an intermediary between Ieyasu and Yodo-Dono. She worked in vain to end their hostilities, and after Yodo-Dono and Hideyori's death, managed to save Hideyori's daughter by putting her in a convent.
The youngest, O-go, married Tokugawa Hidetada, Ieyasu's heir and the second Tokugawa Shogun. They had many children, including the third Shogun Iemitsu, and Kazuko, consort to Emperor Go-Mizunoo. Kazuko's daughter Okiko became Empress Meishō, thus posthumously making Oichi both a grandmother to a Shogun and a great-grandmother to an Empress.