This article explores the complexities of crossing into, and passing as a member of, a national imaginary that conceives of itself through a myth of ethnic homogeneity, or ius sanguinis (‘right of blood’). It analyzes an ethnically Han Chinese Hongkonger’s metapragmatic reflections on her experiences developing a high level of proficiency in Korean and subsequently passing as ethnolinguistically Korean in both Korea and in her homeland of Hong Kong. Her experiences provide an opportunity to reconsider ethnic national identification not merely as ius sanguinis but through an alternative paradigm of ‘ius agendi’, or ‘right of performance’. Understood from the latter perspective ethnolinguistic groups are not static a priori entities but are instead actively ‘disinvented’ and ‘reconstituted’ through the performative practice of what this study terms ‘ethnolanguaging’.