It is known that compared to the mother tongue or the first language, it is much more difficult to master a second language, especially when we learn it after puberty. More time and more effort is needed to learn it, but even so, we can not reach a ``perfect`` level as the mother tongue. To explain this difference, the so-called Critical Period Hypothesis assumes that to master a language we should learn it before the ‘critical period’ and that the brain areas in which language learning is done are different before and after the critical period. However, according to recent neurolinguistic studies, the time of language learning is not the only factor, but the fluency in a language, the proper method of language experience, etc. are also factors that can influence the brain area for languages. In this paper, we argue that to approach to the ‘perfect’ level of a language or to influence the brain area for language, the unconscious ‘imprinting’ of the target language is needed and that the above factors are those that enable this unconscious imprinting. We also propose some methods to facilitate this unconscious imprinting in foreign language learning environment in Korea.