Answer
The answer to the question "For how many years did Tanaka play in the MLB with the Yankees before returning to Japan?" is 8. Tanaka played for the Yankees from 2014 to 2021. He was a very successful pitcher for the Yankees, and he helped them win the World Series in 2017. However, Tanaka decided to return to Japan in 2022 to play for the Tohoku Rakuten Golden Eagles.