Emperor Go-Sai

Nagahito (Japanese: 良仁), posthumously honored as Emperor Go-Sai (後西天皇, Go-Sai-tennō; January 1, 1638 – March 22, 1685), also known as Emperor Go-Saiin (後西院天皇, Go-Saiin-tennō), was the 111th emperor of Japan, according to the traditional order of succession.

Go-Sai's reign spanned the years from 1655 through 1663.

This 17th-century sovereign was named after the 9th-century Emperor Junna and go- (後), translates as later, and thus, he could have been called the "Later Emperor Junna". Emperor Go-Sai could not pass the throne onto his descendants. For this reason, he was known as the Go-Saiin emperor, after an alternate name of Emperor Junna, who had confronted and reached an accommodation with similar issues. This emperor was also called "Emperor of the Western Palace" (西院の帝, Saiin no mikado). The Japanese word go has also been translated to mean the second one, and thus, this emperor might be identified as "Junna II". During the Meiji era, the name became just Go-Sai.

Before Go-Sai's accession to the Chrysanthemum Throne, his personal name (imina) was Nagahito (良仁) or Yoshihito; and his pre-accession title was Hide-no-miya (秀宮) or Momozono-no-miya.

He was the eighth son of Emperor Go-Mizunoo. He was raised as if he were the son of Tōfuku-mon'in; both former Empress Meishō and former Emperor Go-Kōmyō were his older half-siblings.

Emperor Go-Sai's Imperial family lived with him in the Dairi of the Heian Palace. This family included at least 16 sons and 17 daughters, none of whom would ascend to the throne.

Nagahito-shinnō became emperor when his emperor-brother died. This death left the throne vacant and the succession (senso) was received by the new monarch. Shortly thereafter, Emperor Go-Sai is considered to have acceded to the throne (sokui). The events during his lifetime shed light on his reign. The years of Go-Sai's reign correspond with a period in which Tokugawa Ietsuna was the leader at the pinnacle of the Tokugawa shogunate.

Go-Sai married the daughter of the first Takamatsu-no-miya Yoshihito (高松宮好仁親王); and he succeeded as second Takamatsu-no-miya. Then this Imperial prince became the emperor as a temporary measure until his younger brother, Imperial Prince Satohito (識仁親王, Satohito-shinnō) could grow older.