Question: Who is the wife of the elder son of Emperor Akihito and Empress Michiko?

Context articles: Prince Nobuhiko Higashikuni
Prince Hisahito of Akishino
Fumihito, Prince Akishino
Princess Kako of Akishino
Kiko, Princess Akishino
Sayako Kuroda
Empress Michiko
Naruhito, Crown Prince of Japan
Masako, Crown Princess of Japan
Princess Mako of Akishino

Prince Nobuhiko Higashikuni (b. 東久邇 信彦; 10 March 1945）is a Japanese aristocrat.
 The eldest grandson of Emperor Hirohito, he is the eldest son of Shigeko, Princess Teru (the eldest daughter of Emperor Hirohito, and eldest sister of present Emperor Akihito) and Prince Morihiro Higashikuni, a grandson of Emperor Meiji.
 He is nephew of reigning Emperor Akihito.
Prince Hisahito of Akishino (悠仁親王 , Hisahito Shinnō , born 6 September 2006) is the youngest child and only son of Fumihito, Prince Akishino and Kiko, Princess Akishino.
 He is the only grandson of Emperor Akihito and Empress Michiko.
 Hisahito is third in line to become Emperor of Japan, after his uncle Naruhito and his father.
Fumihito, Prince Akishino (秋篠宮文仁親王 , Akishino-no-miya Fumihito Shinnō , born 30 November 1965) is a member of the Japanese imperial family.
 He is the younger son of Emperor Akihito and Empress Michiko and currently second in line to the Chrysanthemum Throne.
Princess Kako of Akishino (佳子内親王 , Kako Naishinnō , born 29 December 1994) is the second daughter of Fumihito, Prince Akishino and Kiko, Princess Akishino, and a member of the Japanese Imperial Family.
 She is the second-eldest grandchild of Emperor Akihito and Empress Michiko.
Kiko, Princess Akishino (文仁親王妃紀子 , Fumihito Shinnōhi Kiko ) , born 11 September 1966 as Kiko Kawashima (川嶋紀子 , "Kawashima Kiko" ) , is the wife of Fumihito, Prince Akishino, the second son of Emperor Akihito and Empress Michiko of Japan.
 She is also known as Princess Kiko.
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 an imperial Shinto priestess of the Ise Grand Shrine, currently serving as the Supreme Priestess.
 She is the youngest child and only daughter of Emperor Akihito and Empress Michiko of Japan.
Michiko (美智子 ) , born Michiko Shōda (正田美智子 , Shōda Michiko ) on 20 October 1934, is the Empress of Japan as the wife of Akihito, the current Emperor of Japan reigning from 7 January 1989.
 She succeeded her mother-in-law, Empress Nagako (Kōjun), consort of Emperor Hirohito (Shōwa).
Naruhito, Crown Prince of Japan (皇太子徳仁親王 , Kōtaishi Naruhito Shinnō , born 23 February 1960) is the elder son of Emperor Akihito and Empress Michiko, which makes him the heir apparent to the Chrysanthemum Throne.
Masako, Crown Princess of Japan (皇太子徳仁親王妃雅子 , Kōtaishi Naruhito Shinnōhi Masako ) , born Masako Owada (小和田雅子 , "Owada Masako" ) on 9 December 1963, is the wife of Naruhito, Crown Prince of Japan, who is the eldest son of Emperor Akihito and Empress Michiko and the heir apparent to the Chrysanthemum Throne.
 She is a member of the Imperial House of Japan through marriage.
 Should the Crown Prince ascend the throne as expected upon his father's abdication, Masako will become empress consort.
Princess Mako of Akishino (眞子内親王 , Mako Naishinnō , born 23 October 1991) is the first child and oldest daughter of Fumihito, Prince Akishino and Kiko, Princess Akishino, and a member of the Japanese Imperial Family.
 She is the eldest grandchild of Emperor Akihito and Empress Michiko.