This chapter analyses foreign wrestlers’ impact on sumo stable performance. Foreign wrestler acceptance varies significantly among stables. Some actively recruit foreigners while others accept only Japanese wrestlers. Data analysis reveals stables with higher foreign wrestler proportions show higher makuuchi wrestler ratios, demonstrating foreign wrestlers’ contribution to stable competitive performance improvement. However, this effect varies by country of origin, with Mongolian-born wrestlers achieving particularly high performance. Sumo stables gain competitive advantage by utilizing foreign wrestlers’ human capital. Comparative analysis with other professional sports markets demonstrates foreign athletes’ unique role in sumo. Sumo sees foreigners reaching the highest rank. This suggests sumo’s technical system is nationality-independent. The stable mistress’s (master’s wife) role is also important, supporting foreign wrestlers’ Japanese cultural adaptation. Globalisation influences sumo stable management strategies. The chapter reveals how traditional organizations adapt to globalisation by strategically deploying diverse human resources, offering insights into diversity management in traditional institutional settings.