<![CDATA[This study examined the acquisition of Indonesian as a second language by native Japanese speakers. Therefore, this study aimed to find out what things affect Japanese speakers in the process of acquiring Indonesian as their second language and to find out which causes are the most dominant in influencing Indonesian language errors by Japanese speakers. The method used in this research is a literature study, then the error data is classified based on the types of errors and the things that affect the error. After that, the data were analyzed descriptively. From the investigation, 31 data were obtained from errors made by a Japanese speaker when communicating. The Japanese speaker experienced natural Indonesian acquisition and did not study Indonesian formally or informally in a particular institution. The data was obtained in the form of group conversations in an online-based application. From these data, it can be understood that the failure of language use that are usually made by native Japanese speakers are related to vocabulary. Common mistakes made are substitution, omission, and addition of letters. In terms of grammar, not so found errors because in terms of sentences are still classified as correct or acceptable in meaning. However, in sentences that use adverbs of time, errors are still found, such as ‘perundang-undangan di sini mau ganti bulan 3 tahun ini’. From a grammatical point of view, there are no errors, but Indonesians do not usually pronounce 'month 3' but only 'Bulan Maret' or 'Maret' only which means March. This is due to the influence of the mother tongue, which usually mentions Sangatsu, which literally translates to the third month. Therefore, it can be concluded that the errors that are commonly experienced by native Japanese speakers are mostly in the vocabulary that undergoes replacement, omission, and addition of letters due to the unfamiliarity of native Japanese speakers in hearing and pronouncing the pronunciation.]]>
