After World War II he was refused entry to Korea, and his Japanese titles were removed by article 14 of the new Constitution of Japan in 1947.

After his death in 1970, Yi Un is alternatively known as Crown Prince Uimin (의민태자), a posthumous name given by the Jeonju Lee Royal Family Association.

The move was meant to ensure that the Korean royal family would not take any further anti-Japanese actions following The Hague Secret Emissary Affair.

[1] Japanese Emperor Meiji, who largely ignored his own grandchildren, devoted a lot of attention to Yi Un, acting as his guardian.

He graduated from the 35th class of the Army Staff College in November 1923 and commanded a battalion of the Guards 2nd Infantry Regiment.

[3] In May 1927, he was sent on an extensive European tour, visiting France, Switzerland, United Kingdom, Belgium, Netherlands, Germany, Denmark, Norway, Sweden, Poland, Austria, Czechoslovakia, Italy, Monaco, and returning to Japan in April 1928.

Under his command, the division relocated to Manchukuo to participate in the Special exercise of the Kwantung Army (actually a mobilization for the possible large-scale conflict with the Soviet Union).

In 1960, President Rhee again denied him permission to return to Korea, but instead offered the prince the position of Korean Ambassador to the Court of St. James's.

In November 1963, President Park Chung Hee granted permission for Prince Yi Eun and Crown Princess Bangja to return to Korea.

In his final years, Prince Yi Eun lived at Nakseon Hall, Changdeok Palace, the former residence of the Korean Imperial Family in Seoul, with Bangja and his younger sister Princess Deokhye.

Approved by the President Park Chung Hee, Yi Un's spirit tablet was put into Jongmyo shrine on 6 May 1973 according to the royal tradition.

After the hotel was demolished in 2013, the building became part of Tokyo Garden Terrace Kioicho, refurbished as a banquet facility, now known as Akasaka Prince Classic House.