This thesis explores the influence of foreign players on the transformation of Japanese rugby over the last three decades. Foreign players first had an impact in company league teams and, more latterly, have also played with distinction in the Japanese national team. Using historical materials and interview data with players, coaches and administrators, I show how the game of rugby in Japan has developed, and consider aspects of the relationship between migrant players and the Japanese game. I follow the actors through the shift from the amateur to the professional period, and describe the impact on Japanese rugby of foreign players and coaches. In the first chapter, I describe the establishment and historical development path of rugby in Japan. The game has incorporated aspects of Japanese styles of organisation, playing techniques and philosophies. Until the 1980s, high school and university rugby was the most popular form of the game, but after then, rapidly-developing company rugby became the predominant domestic form of the game. The company game's latest iteration, launched in 2003, is the Top League, and in it, labour relations have become more professional. Chapter Two describes the influence of foreign players in company teams, looking in particular at migration trends, eligibility rules and labour relations. I found that, as well as increasing in number, foreign players and coaches as teachers are having a deeper influence on the way that Japanese play the game. Chapter Three narrows the focus to a case study of a representative company team, Yamaha Motors. It follows three broad themes, of the history of the team and its moves to a more professional style of organisation, labour relations and the team environment, and the degree of equality between foreign and Japanese players, in terms of salary, social status and the expectations on them. The company teams have a high degree of control over players' contracts, and with salary and expectations differing between professional foreign players, the few Japanese professionals and Japanese players employed as regular employees, the majority, interpersonal relations are still difficult. Chapter Four analyses the case of foreign-born players in the Japanese national team. The eligibility criteria for the Japanese national rugby team do not demand citizenship, only three years' residence, which has caused considerable debate. This chapter found that changes in role that have occurred since the first selection of foreign-born players in 1986, with emphasis of late on adding leadership rather than strength. Through comparative case studies of the national team at three key points in time, 1968, 1999 and 2003, this chapter found that the distinctive Japanese playing style on show in 1968 has now largely disappeared, although moves are underway to revive it. Additionally, players' main loyalties are often now to company teams rather than the national team, and many simply choose not to appear for Japan.