This research aims to investigate how learning English and using it as a tool of self-expression improve learners’ self-confidence. Many scholars have stated that speakers are influenced both consciously and unconsciously by the language they speak, and also by the background culture associated with the language. The author has observed that quite a few Japanese people become more self-expressive and self-confident regardless of their language proficiency when they speak English. In order to see the influence of the language on speakers, the author conducted both quantitative and qualitative research. Though the investigation was preliminary, the results suggest that speakers including beginner-level learners are highly influenced by the language they are speaking and its background culture, with these phenomena affecting their self-expressiveness and self-confidence. In a monolingual country like Japan, where English is not necessary for daily life but it is strongly recommended to acquire it, it is not easy to sustain learners’ motivation. However, if we can utilize English learning as a way to support learners not only to improve their language ability and international awareness but also their self-confidence, there may be more positive outcomes from language learning classes.