Hiro is a wise Japanese engine, who was famously known as the "Master of the Railway", works on The Main Line.
Hiro is wise, very dignified, and enormously kind. He is friendly and is able to find good in any engine he meets. He does not appear to hold a grudge; he helped Spencer after an accident, despite Spencer previously trying to send Hiro to the Sodor Ironworks.
Hiro once lived on a faraway island. He was the strongest engine on his railway, and was famously known as the "Master of the Railway". He was eventually brought to Sodor where he worked for many years. However, he began to show his age, and the works did not have the necessary parts to repair him. To escape being scrapped, he was put on a siding, where he had to wait for the parts to come from his homeland. However, the parts never came and Hiro was all but forgotten.
Thomas eventually found him and, fearing Hiro would be scrapped if he was not Really Useful, promised to bring him back to his former glory while keeping him a secret from Sir Topham Hatt. Thomas also had many of his friends help in the restoration, and Hiro quickly gained their friendship. After breaking down again while trying to avoid Spencer, Hiro was hidden away in another siding, where passing engines visited him and kept him company.
When Sir Topham Hatt found out about the situation, Hiro was brought to the Sodor Steamworks, where Victor oversaw his restoration. Once Hiro was restored, he helped Spencer after his accident, and worked with him and Thomas to finish the Duke and Duchess's Summer House. Despite everything, Hiro had grown homesick, so Sir Topham Hatt arranged for him to be sent back to his homeland.
Hiro eventually came back to Sodor to help the engines with the summer holiday traffic. Upon his arrival, Hiro went to the Steamworks to be examined and then went to Knapford station for his welcome party, which was almost delayed as Thomas was trying to find a welcome present for Hiro instead of telling the other engines about the party. But, Hiro told Thomas that having his friends at the party was the best welcome present. He saw Jobi Wood being delivered to the Docks and told Thomas about where it came from. When Hiro became homesick, Thomas took him to Misty Island, which reminded Hiro of his home.