Until now, much of the research on heritage language (HL) education has focused on the use of oral language or traditional print-based texts by HL speakers who are born and raised in the U.S. In addition, many of the available studies concentrate on beginning-level HL students because few second generation immigrants reach advanced levels of literacy in Korean. Little is known about the use of the HL by individuals who are highly literate in both Korean and English. This paper attempts to address this gap by examining the voluntary writing practices of two adolescent Korean HL speakers with advanced proficiencies in both Korean and English. Through an inductive analysis of multiple data sources (interviews, literacy activity checklists, field notes, and literacy artifacts), this study shows that the two Korean adolescents moved fluidly between their two cultures and languages through their online and paper-based HL writing practices. In addition, their use of Korean in writing helped them socialize with their ethnic peer groups, pursue personal interests, and maintain ties with Korea on a daily basis. These findings inform HL literary instruction and offer insights into the ways HL literacy is situated in the daily lives of biliterate adolescents. (Contains 3 figures and 9 notes.)