This thesis proposes a new ethnic formation in the UK: Anglo-Japanese (A-J). This formation refers to the growing number of young people with one White British and one racially Japanese parent residing in London and South East England. This thesis focuses mainly on the Japanese side of their ancestry which would seem to be underpinned by a pervasive ideological narrative called Nihonjinron (theories of the Japanese). This narrative sets out what it means to be Japanese. The underlying message is that Japan is both mono-racial and mono-lingual and only the so-called racially ‘pure’ Japanese permanently resident in Japan can master the intricacies of Japanese language and cultural practices. This issue is important for the Anglo-Japanese because although they are permanently resident in Britain, they are competent and active participants in a wide range of what might be called traditional Japanese practices, which would appear to contradict the message implied in the influential Nihonjinron ideology. This thesis describes and analyses the cultural practices in which the A-Js engage at Hoshūkō (Japanese Saturday [complementary] school) as well as the dense network of traditional artefacts and associated regulatory practices with which they also engage outside Hoshūkō. This active and intense engagement with Japanese practices in a variety of settings both in Britain and in Japan is very similar to that of Japanese young people in Japan. This engagement not only inculcates the Anglo-Japanese with insider notions of traditional Japaneseness but also inadvertently reinforces the ideological narrative of Nihonjinron. This thesis, influenced by British Cultural Studies, uses an ethnographic perspective to suggest an addition to the development of new ethnicities in contemporary Britain: Anglo-Japanese ethnicities.