Political parties and interest groups represent two important organized political actors in democracies. Much focus has been put on the two, but separately. Yet their interaction also represents a vital party of democracy. The research on party-interest group relationships in western democracies represents a vital part in understanding how democracies work. Research has shown that historically close party-interest group relationships have in many cases declined in strength and that parties in many cases employ less formal ties to a wide variety of interest groups. Still, scholars find variety both across, and within, countries. The clear majority of research done on party-interest group relationships has been conducted on long-lasting democracies in the West, more specifically Western-Europe. This raises the question of whether the same framework, and conclusions, are also valid for long-lasting democracies beyond the geographical scope of the West. In this thesis, I present a case study of seven parties in Japan – the only Asian country to be included in the ranks of long-lasting western democracies. Japan presents an interesting object of study as the country has had a one-party dominance hardly seen in any other long-lasting western democracies. Through this study, I find that while Japanese parties appear to have relationships with a wide variety of interest groups, they are relatively stronger than their western counterparts. At the same time, certain elements within the Japanese context appear not to immediately follow the patterns of the general party population in long-lasting western democracies. Rather, there appear to be qualities of the party organization and the party system in Japan that indicate there still remains a side to party-interest group relationships in Japan that is left uncovered.