It is the first time the 28-year-old has joined a club from outside her home country.
Yamashita said she is “very hungry” and looking forward to the challenge of playing in England’s top flight.
“I’ve won various trophies in Asia, but to level up myself I felt the need to take on a challenge,” she added.
“It’s a famous club that everyone knows, and even now, it feels unbelievable to me.”
Yamashita, who played with City midfielder Yui Hasegawa at Tokyo Verdy, has featured 74 times for her country and has won 17 major honours during her career.
She is the Women’s Super League club’s third Japanese signing of the transfer window following the arrivals of Risa Shimizu from West Ham United and Aoba Fujino from Tokyo Verdy.
