Empress Michiko in the context of "Imperial dynasty"

A dynasty is a sequence of rulers from the same family, usually in the context of a monarchical system, but sometimes also appearing in republics. A "house" is a royal or noble family, not always ruling. Historians periodize the histories of many states and civilizations, such as Ireland (10th century), Roman Empire (27 BC – AD 1453), Imperial Iran (678 BC – AD 1979), Ancient Egypt (3100–30 BC), and Ancient and Imperial China (2070 BC – AD 1912), using a framework of successive dynasties. As such, the term "dynasty" may be used to delimit the era during which a family reigned.

Before the 18th century, most dynasties throughout the world were traditionally reckoned patrilineally, such as those that followed the Frankish Salic law. In polities where it was permitted, succession through a daughter usually established a new dynasty in her husband's family name. This has changed in all of Europe's remaining monarchies, where succession law and conventions have maintained dynastic names de jure through a female.

Naruhito (born 23 February 1960) is Emperor of Japan. He acceded to the Chrysanthemum Throne following the abdication of his father, Akihito, on 1 May 2019, beginning the Reiwa era. He is the 126th monarch, according to the traditional order of succession.

Naruhito was born during the reign of his paternal grandfather, Emperor Hirohito. He was the first child of Crown Prince Akihito and Crown Princess Michiko (later Emperor and Empress). His father acceded to the throne in 1989 upon the death of Emperor Hirohito, making Naruhito the heir apparent. He was formally invested as Crown Prince of Japan in 1991. He attended Gakushūin schools in Tokyo and later studied history at Gakushuin University and English at Merton College, Oxford. In June 1993, he married the diplomat Masako Owada. They have one daughter: Aiko, Princess Toshi.

Sayako Kuroda (黒田 清子, Kuroda Sayako; born 18 April 1969), formerly Sayako, Princess Nori (紀宮清子内親王, Nori-no-miya Sayako Naishinnō), is the youngest child and only daughter of Emperor Emeritus Akihito and Empress Emerita Michiko, and the younger sister of the current Emperor of Japan, Naruhito. She is an imperial Shinto priestess of the Ise Grand Shrine, currently serving as the Supreme Priestess.

Kuroda held the appellation "Nori-no-miya" (Princess Nori), until her marriage to Yoshiki Kuroda on 15 November 2005. As a result of her marriage, she gave up her imperial title and left the Japanese imperial family, as required by the Article 12 of the Imperial Household Law, and received a payment of approximately US$1,000,000.