Tadashi was a Japanese teenager who worked for Dom Cobb, helping him extract secrets from Saito's mind.
On the bullet train to Tokyo, Cobb, Arthur, Nash and Tadashi sedated Mr Saito with the intention of sharing his dreams. Tadashi stayed awake to control the machine that put the other men under. About 30 seconds before they were due to wake up, Tadashi put headphones on Nash and played "Non, je ne regrette rien" to alert him to the time. The three extractors then woke up, and began arguing as the job was a failure. Cobb threw Tadashi some money and told them it was every man for himself, as he rushed to leave the train. Nash and Arthur then exited the cabin, leaving Saito to wake up and see only Tadashi reading his comic.