Native language transfer plays a crucial role in second language acquisition, often leading to errors influenced by the first language. This paper investigates the causes of Japanese learners' errors in using the auxiliary particles “も” and “ でも” in their written compositions, focusing on both semantic and syntactic levels. This study reveals that learners may omit the particles “も” or “でも” due to ineffective information processing within the sentence, thereby hindering the positive transfer from their native language. Japanese learners' tendency to mix the usage of “も” and “ でも” may stem from negative transfer at the semantic level or from the combined influence of native language transfer at both the semantic and syntactic levels.