The 23-year-old became the first Japanese male to reach the last 16 at Roland Garros since 1938 as he beat home player Benoit Paire 6-3 6-7 (3-7) 6-4 6-1.
United were forced to play the last 16 minutes without young Brazilian defender Rafael, who received a second yellow card for a foul on Benoit Assou-Ekotto, but they survived as Spurs were unable to muster the attacking threat that has made them such an impressive force at home and abroad this season.