This study aims to demonstrate the need for learner-corpus-informed applications and proposes methods of application that promote the proper use of Korean topic and nominative markers. This study extracted 3004 pieces of error from the error-annotated corpus of the "Korean Learners' Corpus," the largest Korean learner corpus to date. A detailed examination of the above data was conducted to subdivide the types of substitution errors related to the topic and nominative markers, and to analyze the error rate according to the type of error and level of proficiency. The statistical data revealed no consistent correlation between the error rate and proficiency level. Furthermore, based on the proportion of error types by proficiency level, this study proposes the use of common mistake boxes with real errors; these errors are generally committed by learners of all proficiency levels and are not presumed problematic by grammarians or intuition-based teachers. These boxes can, therefore, be utilized as a practical tool for inclusion in pedagogical materials, such as learner's dictionaries and textbooks.