Bernardo Silva fed De Bruyne for the game's opener in front of 65 000 fans at Nissan Stadium, just outside Tokyo, as the Belgian cut inside and unleashed a powerful shot with his left foot.
Keita Endo scored a surprise equaliser for Yokohama before De Bruyne released the pace of Sterling, who made no mistake as he slotted past the goalkeeper with two defenders in pursuit.
The fast-paced first half gave way to a slower second period, with a few missed chances for both sides including an attempt by Sterling in the 58th minute that was ruled out for offside.
Kazaki Nakagawa was denied by City goalkeeper Claudio Bravo before Nmecha, 20, bundled in the visitors' third goal in the final minute after a cross from 18-year-old Adrian Bernabe.
The victory ended a sometimes difficult Asian tour for Pep Guardiola's City, who kicked it off by arriving two days in China and faced criticism in Chinese state media forRead More
