In 1930, he a biology teacher at Songdo Middle School and worked there for 10 years.
Japanese scientists said that there were 921 species of Korean butterflies[2] but he made a great effort to collect 160 mil of cabbage butterflies throughout the Korean peninsular[3] and compared their patterns and measured the length of front wings with a ruler by himself.
He drew a conclusion that even though the wing patterns are different, they might not be different species and got rid of many wrong scientific names posted by Japanese prematurely and proved that they are individually changed adapting to surroundings and classified Chosun butterflies into 248 species.
When the Korean War broke out, he tried hard to keep his samples and maps so he couldn't escape Seoul.
He wrote a small dictionary Lernolibro de Esperato Kun Vortaeto 1947 because he was deeply involved in international peace movement to resist Japanese imperialism.
During the Korean War, he was mistaken as one of North Korea's People's Army and got shot by a drunken man, in front of a theater in Seoul while he was going to the national museum which was burnt by a bombing attack.