Team teaching is an established concept in Asian countries; it comprises teachers who are native or fluent English speakers (Assistant Language Teachers: ALTs), and foreign language teachers working together. Research on ALTs has so far focused mainly on the impact of team teaching on teachers and learners, or on the perceptions and attitudes of students, but few studies have examined the aspects of teachers’ reflections on team teaching in Japan. Against this background, this chapter aimed to explore the experiences of an ALT practicing collaborative language teaching with Japanese teachers of English in Japan. It also examined how reflection transformed his perception of English teaching with JTEs. Specifically, using a narrative research method, the transformation of the ALT’s perceived identity during his teaching experience was determined through three semi-structured interviews on (1) his pre-teaching experience; (2) nine months after he became accustomed to teaching in Japan; and (3) eight months after he acquired more teaching experience. His narratives were visualised in the conceptual relational diagrams through qualitative analysis, and the diagrams demonstrated the significance of his life story: the process of engaging in the community through access to imagined community and recognition of the self that is here now.