Decades-long researches in a language in contact field have proved that when a learner learns a new language, his/her knowledge regarding their first language might interfere with their learning. If it occurs, the learning process will be more challenging. The data in this research was collected by using document study technique on twenty-five…

There have been many studies on first language interference towards learners' second or foreign language learning, but not many on the otherwise. This study investigates the effects of learning Japanese as a foreign language towards learners' first language use, Indonesian. The data for this qualitative study were obtained from five Japanese…