Masahiro Tanaka
Sakamoto was born in Itami, Hyōgo, and began playing baseball while in the first grade at Koyanosato Elementary School for the Koyanosato Tigers (a Little League team) alongside current New York Yankees pitcher Masahiro Tanaka. Ironically, Sakamoto was the team's ace pitcher, and Tanaka his batterymate on the team. Both Sakamoto and Tanaka went on to attend Itami Municipal Matsuzaki Junior High School, but Sakamoto opted to join Itami Senior, while Tanaka chose to play for the Takarazuka Boys.