Yi Un Lieutenant General Prince Imperial Yeong , the Crown Prince Uimin ( also Euimin ) , also known as Yi Un , Yi Eun , Lee Eun , and Un Yi ( 20 October 1897 – 1 May 1970 ) , was the 28th Head of the Korean Imperial House , an Imperial Japanese Army general and the last crown prince of Korea . The prince was born on 20 October 1897 at Deoksu Palace in Seoul as the seventh son of Gojong , the Gwangmu Emperor . His mother was the Honorable Princess Consort Eom Seon - yeong , a palace attendant , who was posthumously awarded the title of Princess Sunheon . He was also the younger half - brother of Emperor Sunjong and Prince Imperial Ui . He was titled " Prince Imperial Yeong " in 1900 , and became the crown prince in 1907 , despite being younger than Prince Ui . Prince Ui ' s support base at court was not strong because his own mother , Lady Jang , had already died . In December 1907 , he was taken to Japan on the pretext of receiving a modern education . He was enrolled at Gakushūin and the Imperial Army Academy , both in Tokyo . Graduating from the academy on 25 May 1917 , he was commissioned a second lieutenant in the infantry on 25 December , and steadily rose up the ranks , receiving promotions to lieutenant ( April 1920 ) , captain ( July 1923 ) and to major ( August 1928 ) . In 1920 he married Princess Masako of Nashimoto ( born 4 November 1901 – ) , the eldest daughter of Prince Nashimoto Morimasa , on 28 April 1920 at Tokyo . In 1910 , when Korea was annexed by Japan and Emperor Sunjong was forced to abdicate , he was titled " His Royal Highness Crown Prince of Korea " . On 10 June 1926 , upon the death of Emperor Sunjong and his funeral , he became " King Ri of Korea " ( demoted Korean sovereign ' s title after the Japan - Korean Annexation Treaty ) . Prince Yi Eun ( also known as Prince Ri Gin in Japan ) served in the Japanese Army as Commanding Officer of the 59th Regiment , the 4th Depot Division , and then later the 51st Division . He received further promotions to lieutenant colonel ( August 1932 ) , colonel ( 1 August 1935 ) , major general ( 15 July 1938 ) and to lieutenant general ( 2 December 1940 ) . He also served in the Imperial Japanese Army Air Force with the rank of lieutenant general , commanding 1st Air Army . He further served as Instructor at Military Staff College , attached to the Inspectorate General of Military Training and became a Member of the Supreme War Council during wartime . After Korea became independent of the Empire of Japan in 1945 , he requested permission from President Syngman Rhee to be allowed to return to Korea with his family , but was refused . The prince was offered the position of Korean Ambassador to the Court of St . James in 1960 , but refused on the grounds of illness . In November 1963 , President Park Chung - hee granted permission for him and his wife , Crown Princess Bangja , to return to Korea . By that time he was an unconscious from cerebral thrombosis . He received treatment at St . Mary ' s Hospital in Seoul . In his final years , he lived at Nakseon Hall , Changdeokgung Palace , the former residence of Imperial house in Seoul , with Bangja and his younger sister Princess Deokhye . Seven years after returning to his country , he died on 1 May 1970 at Nakseon Hall , Changdeok Palace , Seoul . He was buried at Hongyureung in Namyangju , near Seoul and is known posthumously as Crown Prince Euimin of Korea .