Based on qualitative and interpretive methodology, this book illustrates how Japanese L2 English users establish identities related to L2 English as part of their multiple identities, and how they explore new identity options through ELF. Moreover, the author demonstrates how power relations relating to English language are constructed through the participants' experiences in ELF interactions. Also, analysis of the data reveals that to what degree the Japanese L2 English users wish to affiliate with particular groups in ELF interactions with people from diverse cultural background.