This paper firstly examines the concepts of language and culture from the perspective of knowledge. Knowledge is understood as the total of explicit knowledge, implicit knowledge, and tacit knowledge. Both language and culture are included in knowledge; their non-detachability is expressed in phrases like language is a part of culture, two sides of the same coin, language is the core of culture, and languaculture. We point out that tacit knowledge has two parts in L 2 education. One part can be changed to explicit knowledge using metaphor or analogy, and the other part cannot be completely converted to explicit knowledge. We can learn the latter only by experience. We created an E-learning system to help students to learn tacit nuance of Japanese onomatopoeia. Students can learn explicit nuance by studying word-formation rules, creating onomatopoeias, getting narrative feedback to modify their linguistic hypotheses, and then acquiring the new nuance they did not notice before. In the process of repeated learning, learners will also be aware of tacit nuances which cannot be changed to language, as they internalize the new concept and output it again in the practice of their learning experience.