This presentation will describe a framework for a longitudinal L2 motivation study based on a three-year voluntary ER circle project co-hosted by four private universities in Japan. Drawing on Dörnyei’s complex systems theory, we have employed a mixed approach that integrates both quantitative and qualitative analyses of learners’ motivational changes over the long term. We will make an interim report of our analyses and discuss challenges ahead both in terms of educational practice and research design. So far, a quantitative analysis of periodical questionnaires shows an increase in the comfort level of the participants while a decrease in the anxiety level. However, the descriptive statistics of the reading data show an overall decline in reading amount, which indicates difficulties in maintaining long-term motivation. Individual-based qualitative analyses of questionnaire surveys as well as personal interviews are employed to identify the motivational and demotivational factors.