Tominaga joined the company in 2002 and initially worked in the EAD Department. His first work was as assistant director in The Legend of Zelda: The Wind Waker, where he helped with the positioning of treasure boxes, items and enemies. Following this, he wrote the text messages in Mario Kart: Double Dash!!, where he also coordinated with NOA and NOE to ensure that the game had an almost global release. Afterwards, he was the sequence director of Super Mario 64 DS, where he designed the system flow of the title under the guidance of Shigeru Miyamoto.
Later on, Tominaga directed the field puzzle design on Twilight Princess, the minigame section of Wii Fit Plus, and the planning for the Eldin Volcano and the Earth Temple dungeon in Skyward Sword. He later became the planning leader of A Link Between Worlds and Breath of the Wild; with the Expansion Pass DLC of the latter (comprising of The Master Trials and The Champions' Ballad), Tominaga was appointed as director.