Rounding the Bases offers the first comprehensive history of Japanese Little League, tracing its origins near U.S. military bases in the 1950s to its rise as one of the world’s most successful youth sports programs. Drawing on interviews with American and Japanese figures, along with diverse archival materials, the book uncovers overlooked individuals and forgotten facts, including early organizational challenges and uneven World Series participation after its 1964 founding in the Tokyo metropolitan area. The emergence of the West Tokyo league and a strong regional association in Osaka contributed to World Series championships in 1967 and 1968. Lasting corporate support for Japanese Little League from Mitsui Bussan and Fuji-Sankei followed. The narrative unfolds at ground level—detailing who did what, when, and why—while situating Little League within the broader landscape of Japanese baseball, from nanshiki rubber-ball leagues to school teams to the professional game. The book challenges cultural stereotypes and highlights structural differences from the American model. It also explores how this U.S. import intersected with postwar Japanese history: Cold War cultural policy, revived national pride and a return to bushido (Samurai moral code) ideals, growing middle-class affluence and corporate influence, and more liberal societal attitudes in the late twentieth century. Rounding the Bases is a unique contribution to baseball history and will appeal to both casual fans and serious scholars of the game.