The present study investigates the semantic differences between the Korean adjective 불편하다 and the Japanese expression 不便だ, focusing on how learners can achieve more accurate translations. Although 불편하다 is often translated as 不便だ, their semantic ranges differ, especially regarding psychological discomfort, where mistranslations frequently occur. The study analyzed student writings from 2024 and conducted a 2025 instructional activity advising students to avoid using 不便だto assess its impact on translation accuracy. Results showed that overuse of 不便だwas common, and targeted instruction improved accuracy. However, learners still faced challenges expressing psychological discomfort in Japanese due to limited vocabulary. These findings highlight the importance of teaching lexical nuance and expanding vocabulary to enhance translation accuracy between Korean and Japanese.