This paper focuses an the problem of language transfer in foreign language learning. The transfer caused by the difference between learner's mother language and target language, often leads a communicative gap. This paper first analyzes the semantic relations between learner's mother language and target language. Then proposes a CGM (Communicative gap Model) due to language difference. We have developed a communicative language-learning environment called Neckle (Network-based Communicative Kanji Learning Environment) to support foreign language learning through communication with native speakers. Neckle has a software agent that observes the conversation between the learner and the native speaker, checks up the communicative gap according to CGM, and notices the gap for the support of language learning congenial to each learner. Learners can not only be aware of the language difference but also acquire its cultural background from the native speakers.