This article explores the prevalence of large age gaps in Japan and the factors that influence them. The average age gap between partners is approximately 7 years for men and 5 years for women, with social norms, economic factors, and educational levels playing a role in determining the size of an age gap. Gender roles also play a role in influencing how much difference there is between partners’ ages when entering into relationships or marriages. Ultimately, understanding these influences can help us gain insight into why certain couples choose certain sizes for their respective ages gaps.