People in Japan can still fondly recall that, at the Rugby World Cup in 2015, the Japan team had three wins for the first time ever in the history of the event. This was something that really excited Japan. A main topic of media coverage comparable to this very accomplishment was the fact that so-called, "foreigners" were included in the Japanese team. Opinions on this in Japan were both positive and negative. The negative viewpoints involved, "As they represent Japan, they have to be Japanese," while the positive viewpoints voiced acceptance, considering that, "As they are competing for Japan, nationality or place of birth has got nothing to do with it." Each sport has its own rules about what types of people can represent a country, but eligibility rules to play for national representative teams are different than those of the Olympics, requiring actual nationality. It is stated that a player may only play for a country’s representative rugby team if they were born in that country, one of their parents or grandparents were born in the country, or they have lived in the country in question for 36 consecutive months, and that if they satisfy any of these three conditions, they can represent a country in an international competition. Tsuyoshi Matsushima questions, "However, have we ever considered as to when, where, and for what this rule was established and by whom in the first place?"

Let's get back to the initial discussion. In his study, Matsushima also clarified how the eligibility rules to play for national representative teams originated and how such have been changed, which reveals that the source of the current eligibility rules was a decision made at World Rugby in 1892. This involved solving a problem regarding eligibility between the members of that time, along with England and Scotland and the issue of the treatment of residents from British colonies living in the U.K. At this juncture, differences of nationalities or other countries such as Japan were not even considered. "That caused an argument about multinational and multiethnic team formations in Japan in the 1990s and afterwards, and as a result, the Japan rugby team has become a mechanism to embody the image of Japanese people based on diverse nationalities at the World Cup and that of Japanese people based on Japanese nationality at the Olympic Games," Matsushima explains.

As rugby poses questions about nationalism, such as "What is a Japanese person?" and "What shape should our country take?", sports exposes aspects and issues of modern society and creates a future regardless of being right or wrong. Matsushima concludes, "That is what makes it so interesting."