In Japanese colonial-era Korea, Sōshi-Kaimei was applied from 1940. This was a policy of pressuring Koreans to adopt the Japanese paternalistic family system instead of their own traditional clan system. While Sōshi (creation of family names) was almost compulsory, Kaimei (change of given names) was voluntary. It is the general opinion of previous research that the Governor General of Chosen had actively promoted Sōshi but was passive about Kaimei, because it was necessary to leave a boundary line between Koreans and Japanese. However, there is documentation that some Korean women in Keijō changed their given names to Japanese-style ones ending with ko (Chinese character 子), from the 1930s. Additionally, some Korean girl students using ko in their given names were found on the register of Dongnae Girls’ High School in Busan. When Sōshi-Kaimei was implemented, Japanese-style names became more popular, and the use of ko in given names also increased among Dongnae students. A portion of the school register records that some of those who kept their Korean names were called by Japanese-style ko names, by their close friends at school. When students could not use Japanese-style names due to opposition from their patriarchs, they chose such names for themselves to be used with in their spheres of intimacy. This trend reveals how Korean girl students using ko in their names may have reflected a kind of “voluntary” consent to colonial power.