[2] On May 31, 2018, Kuwahara pitched his debut game in the interleague play against the Hokkaido Nippon-Ham Fighters.

[3] On June 14, in the interleague play against the Fukuoka SoftBank Hawks, he became the winning pitcher for the first time.

on July 4, 2020, he became the winning pitcher for the first time in two years in a game against the Chunichi Dragons, but on August 12, he fractured his right elbow and underwent surgery.

[5][6] On December 8, 2020, the Giants re-signed him as a developmental player with an estimated salary of 13.2 million yen.

In 2023 season, Kuwahara only had a chance to pitched five games in the first league, and the Giants released him on October 28.