Inspection Mission to Japan
Park Jeong-yang, Eo Yun-jung, Hong Yeong-sik and others travelled secretly to Japan to study its government and industry; Yu Gil-jun stayed on to study.

Academy of Korean Studies · Public domain · Source
In 1881 the government sent some sixty men to Japan — twelve commissioners, including Park Jeong-yang, Eo Yun-jung and Hong Yeong-sik, and their aides. To avoid conservative outcry they left under cover as secret royal inspectors of Dongnae. Over some four months each commissioner studied a ministry such as Home Affairs, Foreign Affairs, Finance or the Army, and they also toured customs houses, the mint and factories before submitting their reports.
Their findings underpinned the reforms led by the Office for Extraordinary State Affairs. Of the aides, Yu Gil-jun and Yun Chi-ho stayed on in Japan to study. The mission was once called the "gentlemen’s sightseeing group".