This article provides an overview of the recent immigrant phenomenon in Japan and explains the complexity of the social integration (SI) of Nikkei Brazilians. Through the research, factors that explain the degree of social integration (SI) of Nikkei Brazilians are identified. Basic data include triangulated results from a survey of 80 people and interviews with 8 individuals. This mixed method case study presents a formula for assessing the degree of SI (SI score), empirically tests and questions several key hypotheses derived from previous literature, and explores the possibility of developing a new non-conventional theory to explain this phenomenon.