This study examines the concept of Korean ethnicity by looking into how the Choseonjok, ethnic return migrants from China, are perceived in online news comments. Data were collected from 3,109 comments, which were written in response to 28 news articles regarding the Choseonjok, and analyzed using a Python-based text-mining technique and critical discourse analysis. The findings show that the commenters perceived the Choseonjok negatively, including as potential criminals or social vice. They not only placed the Choseonjok in an inferior position to pure Koreans but also excluded them from the category of compatriots, arguing that speaking the same language and sharing a similar appearance were not enough to make the ethnic return migrants Korean compatriots. This study critically demonstrates how a group of ethnic return migrants is depicted in online public discourses and how this portrayal can shed light on the conceptualization of Korean ethnicity in this era of multiculturalism.