In this chapter I introduce the Direct and Indirect Effect Model of Reading (DIER), an integrative theoretical framework designed to explain reading development across languages, and examine its application in Korean. DIER posits that successful reading comprehension relies on a multitude of interdependent skills and knowledge, including executive functions, orthography, phonology, morphology, vocabulary, grammatical knowledge, higher-order cognitive abilities, background knowledge, and socio-emotional aspects. A review of evidence from Korean-speaking children supports the model's component skills hypothesis and hierarchical relations hypothesis. Despite substantial research on reading development in Korean, however, gaps also remain, particularly in understanding text-level reading and the structural relations among component skills. I also discuss the implications of DIER for assessment and teaching, emphasizing the need for targeted, integrated instruction tailored to individual student needs and developmental phases.