We held a Japanese language class for foreign students called "Reflecting on Japanese language learning through a portfolio". The portfolio included setting a learning objective, recording the learning process, and measures meant to encourage self-reflection. As part of the class, we held sessions for exchanging opinions on a variety of topics, starting from the notes in the portfolios. In this paper, we focus on one of the learners and analyze her portfolio, end-of-term paper, questionnaire responses, and interview answers. As a result, it has become clear how the learner has come to reframe her learning behavior, the changes in her perceptions of learning and the results of these changes, as well as her personal connection with Japanese language. Thus, we were able to support with data the effectiveness of the portfolio activity.