This study investigates the growth trajectory of the Japanese business group Sumitomo, challenging previous research that used the ‘big push’ concept to explain the expansion of Japanese business groups. Rather than relying on government assistance, as the big push concept suggests, Sumitomo successfully diversified into different business sectors by leveraging its existing resources and financial networks. This led to an unintentional but effective expansion into the finance, warehousing, and real estate sectors. Sumitomo’s case underlines the importance of exploring additional context-specific factors in business growth, moving beyond the conventional application of the big push concept. The findings of this study will prompt future research to re-evaluate the growth patterns of business groups with minimal government aid, particularly in regions distant from government control, to foster a more nuanced understanding of a country’s business landscape.