The Japan-Korea Annexation Treaty (1910): The Emperor of Korea and the imperial family were entitled to suitable honorific titles, authority and honor, and in accordance with the Act, which acknowledges the former Emperor of Korea as King, establishes titles for each prince, future successor, and the empress, and treats them with courteous reception, the status of 'king' was granted to the former emperor of Korea, a system known in Japanese as Okozoku.
韓国併合ニ関スル条約（1910年）韓国皇帝及び韓国皇族に相当な尊称、威厳及び名誉を享有させること等が約され、s前韓國皇帝ヲ册シテ王ト爲シ皇太子及將來ノ世嗣、太皇帝及各其儷匹ノ稱呼ヲ定メ竝ニ禮遇ノ件により、前韓国皇帝に対して「王」の身分が与えられる等した（王公族制度）。