[1] He has previously played in NPB for the Hokkaido Nippon-Ham Fighters and in Major League Baseball (MLB) for the Boston Red Sox.

[5] On January 11, 2024, Uwasawa signed a minor league contract with the Tampa Bay Rays.

[6] On March 27, after triggering an assignment clause in his contract, he was traded to the Boston Red Sox in exchange for cash considerations.

[8][9] On April 28, Uwasawa was recalled from the Triple-A Worcester Red Sox and promoted to the majors for the first time.

[14] On December 18, 2024, Uwasawa signed a four–year contract with the Fukuoka SoftBank Hawks of Nippon Professional Baseball.