Tokugawa Iemitsu in the context of "Wet nurse"

Sakoku (Japanese: 鎖国; IPA: [sa̠ko̞kɯ̟]; lit. 'chained country') was the isolationist foreign policy of the Japanese Tokugawa shogunate under which, during the Edo period (from 1603 to 1868), relations and trade between Japan and other countries were severely limited, and almost all foreign nationals were banned from entering Japan, while common Japanese people were kept from leaving the country. The policy was enacted by the shogunate government (bakufu) under Tokugawa Iemitsu through a number of edicts and policies from 1633 to 1639.

Japan was not completely isolated under the sakoku policy. Sakoku was a system in which strict regulations were placed on commerce and foreign relations by the shogunate and certain feudal domains (han). There was extensive trade with China through the port of Nagasaki, in the far west of Japan, with a residential area for the Chinese. The policy stated that the only European influence permitted was the Dutch factory at Dejima in Nagasaki. Western scientific, technical and medical innovations flowed into Japan through Rangaku ("Dutch learning").

Nikkō (日光市, Nikkō-shi; IPA: [ɲikkoꜜːɕi]) is a city in Tochigi Prefecture, Japan. As of 2 December 2020, the city's population was 80,239, in 36,531 households. The population density was 55 persons per km. The total area of the city is 1,449.83 square kilometres (559.78 sq mi).

Nikkō is a popular destination for Japanese and international tourists. Attractions include the mausoleum of shōgun Tokugawa Ieyasu at the Nikkō Tōshō-gū shrine, and that of his grandson Tokugawa Iemitsu (Iemitsu-byō Taiyū-in), along with Futarasan shrine, which dates to the year 767. There are many famous onsen (hot springs) in the area. Elevations range from 200 to 2,000 meters.

Oeyo (於江与), Gō (江), Ogō (小督) or Satoko (達子) : 1573 – September 15, 1626) was a noblewoman in Japan's Azuchi–Momoyama period and early Edo period. She was a daughter of Oichi and the sister of Yodo-dono and Ohatsu. When she rose to higher political status during the Tokugawa shogunate, she took the title of "Ōmidaidokoro". Following the fall of the Council of Five Elders, Oeyo and her sisters were key figures in maintaining a diplomatic relationship between the two most powerful clans of their time, Toyotomi and Tokugawa. Due to her great contributions to politics at the beginning of the Edo period she was posthumously inducted into the Junior First Rank of the Imperial Court, the second highest honor that could be conferred by the Emperor of Japan.

Oeyo married three times, first to Saji Kazunari, her cousin, then to Toyotomi Hideyoshi's nephew, Toyotomi Hidekatsu. She had a daughter with Hidekatsu named Toyotomi Sadako, who later married Kujō Yukiie. Her third and last husband Tokugawa Hidetada became the second Tokugawa shōgun. She was also the mother of his successor Iemitsu, the third shōgun. Her children included Senhime, Tamahime, Katsuhime, Hatsuhime, Takechiyo (Iemitsu), and Tadanaga. Hatsuhime was adopted by Oeyo's sister Ohatsu, who was married to Kyōgoku Takatsugu.

Lady Kasuga (春日局, Kasuga no Tsubone; 1579 – October 26, 1643) was a Japanese noble lady and politician from a prominent Japanese samurai family of the Azuchi–Momoyama and Edo periods. Born Saitō Fuku (斉藤福), she was a daughter of Saitō Toshimitsu (who was a retainer of Akechi Mitsuhide). She was the wet nurse of the third Tokugawa shōgun Iemitsu. Lady Kasuga was one of the best politicians in the Edo period. She stood in front of negotiations with the Imperial Court and contributed to the stabilization of the Tokugawa Shogunate.

Kasuga was one of the most powerful figures in the Ōoku (the quarters in Edo Castle where the women related to the Shogun family resided) . She is counted alongside Matsudaira Nobutsuna and Yagyu Muneyori as one of the Three Tripod Legs, who supported and propped up Iemitsu.

Tokugawa Tsunayoshi (徳川 綱吉; 23 February 1646 – 19 February 1709) was a Japanese samurai, daimyo and the fifth shōgun of the Tokugawa dynasty of Japan. He was the younger brother of Tokugawa Ietsuna, the son of Tokugawa Iemitsu, the grandson of Tokugawa Hidetada, and the great-grandson of Tokugawa Ieyasu.

Tsunayoshi is known for instituting animal welfare laws, particularly for dogs. This earned him the nickname of "the dog Shogun" (Inu-Kubō 犬公方: Inu=Dog, Kubō=formal title of Shogun).

Enryaku-ji (延暦寺, Enryaku-ji) is a Tendai monastery located on Mount Hiei in Ōtsu, overlooking Kyoto. It was first founded in 788 during the early Heian period (794–1185) by Saichō (767–822), also known as Dengyō Daishi, who introduced the Tendai sect of Mahayana Buddhism to Japan from China. The temple complex has undergone several reconstruction efforts since then, with the most significant (that of the main hall) taking place in 1642 under Tokugawa Iemitsu. Enryaku-ji is the headquarters of the Tendai sect and one of the most significant monasteries in Japanese history. As such, it is part of the UNESCO World Heritage Site "Historic Monuments of Ancient Kyoto (Kyoto, Uji and Otsu Cities)". The founders of Jōdo-shū, Jōdo Shinshū, Sōtō Zen, and Nichiren Buddhism all spent time at the monastery. Enryaku-ji is also the center for the practice of kaihōgyō (aka the "marathon monks").

The Ōoku (大奥, "great interior") was historically the women's quarters of Edo Castle, the section where the women connected to the reigning shōgun resided. Similar areas in the castles of powerful daimyō, such as the Satsuma Domain, were also referred to by this term.

During the reign of the second shogun, Tokugawa Hidetada, Ōoku was established in Edo Castle as a women's room where his official wife (御台所, Midaidokoro), Oeyo, resided. During the reign of the third shogun, Tokugawa Iemitsu, the Ōoku was expanded at the suggestion of his nanny, Lady Kasuga, to ensure the birth of a male heir to the shogun's lineage, and became a vast shogun's harem with nearly 1,000 women working as maidservants.

Matsudaira Nobutsuna (松平 信綱; December 19, 1596 – May 4, 1662) was a Japanese daimyō of the early Edo period, who ruled the Kawagoe Domain. First serving Tokugawa Iemitsu as a page, Nobutsuna was renowned for his sagacity. He was named a rōjū in 1633. Nobutsuna led the shogunal forces to their final victory over the rebellion at Shimabara. His court title was Izu no Kami, which was the origin of his nickname, "Izu the Wise" (知恵伊豆, Chie Izu).