Hwanguk (Korean: 환국; Hanja: 桓國) is the first mythical state of Korea claimed to have existed according to Hwandan Gogi.
In the original footnotes for the book, Il-yeon clarifies the meaning of the 桓因 as Jeseok (帝釋, Korean Buddhist name for Indra).
"[1]However, these misreadings were not common thanks to the footnotes, as evidenced by the quotes from other literature such as the Veritable Records of the Joseon Dynasty,[1] In 1918, Korean historian Choe Nam-seon claimed Hwanguk means "heaven" and is the abode of the Hwan people, which he reflected in his 1927 translation of Samguk Yusa (Choe later changed his opinion in 1954).
[1] In the 1921 edition of Samguk Yusa published by Kyoto University, an act of correction was conducted to clarify the character as 因, which brought backlash from Korean nationalists leading to the adoption of the misquote as a mainstream interpretation among Korean historians in the early 20th century.
[1] In 1966 Korean pseudohistorian Moon Jeong Chang claimed in his work Dangunjoseonsagiyeongu ("Research of Historic Records of Dangun Joseon") that the Japanese authorities tried to suppress the truth of Hwanguk by forging historic documents, led by Japanese historian of Korea Imanishi Ryu (今西龍).