is a retired Japanese professional baseball outfielder. He played for the Chunichi Dragons of the Nippon Professional Baseball(NPB).
In the 2015 off-season he along with team mates Iori Katsura, Shuhei Takahashi, Tomohiro Hamada and Junki Kishimoto were loaned to the Taiwanese winter league
Along with teammates Shun Ishikawa and Takuya Kinoshita, Tomonaga was selected for the Western League representative team for the 2016 Fresh All-Stars game in Okayama. Tomonaga started in centre-field, batting 3rd in the line-up and recorded 1 hit in 4 at-bats.
On December 2, 2019, he become free agent.
Bold indicates league leader; statistics current as of 29 September 2016