At age sixty, Shyu was the youngest of the five Fire Sages that guard the Fire Temple on Crescent Island. Shyu helped Aang speak with Avatar Roku in "Winter Solstice Part 2: Avatar Roku". For this reason, he was removed from his position and imprisoned.
When a beacon lit in the sky (seen in "The Southern Air Temple") and the eyes of the statue of Avatar Roku began to glow several weeks before Aang's arrival on Roku's temple, the Fire Sages all knew the Avatar had returned. Unlike his colleagues, Shyu chooses to help the Avatar, knowing that the other sages obey the will of Fire Lord Ozai.
After a failed attempt to open a locked chamber containing Avatar Roku's statue, Shyu aids Aang by tricking the other sages into believing Aang had already opened the chamber. The sages open the door and Aang is able to enter before they can catch him; the chamber is sealed shut by a white light. Shyu is quickly labeled a traitor for believing that it is the Sages' duty to protect the Avatar rather than of remaining loyal to Fire Lord Ozai. When Aang emerges again, possessed by Avatar Roku, Shyu orders Katara and Sokka to leave before Roku destroys the temple. The two refuse until they have rescued Aang.
At the end of the "Winter Solstice Part 2: Avatar Roku", it is revealed that Shyu was among the five Fire Sages captured and imprisoned by Zhao; although he is the only one loyal to his original calling in his disobedience to the Fire Nation's cause, both he and his colleagues are categorized by Zhao as traitors. Shyu's ultimate fate is unknown.
Shyu's background goes back a long way, as he comes from a proud lineage of sages. His grandfather, Kaja, was the very first who declared against popular belief that the Avatar had managed to survive the initial assault on the Air Temples, a determination that he passed on to his son. This was accounted as treason against the Fire Lord and Shyu's father was branded a traitor and sent away never to be seen again, leaving Shyu orphaned and to be raised by the other sages. Despite firsthand knowledge of the price of betraying the Fire Lord, Shyu still chooses not to blindly follow him, and instead remains loyal to the Avatar.
He was arrested by Admiral Zhao at the end of "Winter Solstice Part 2: Avatar Roku". He was probably released after the war ended. It is possible that he was among the Sages who crowned Zuko as Fire Lord, though it was not he who placed the headpiece.
With the exeption of Avatar Roku, Shyu is the first Fire Nation born ally of Team Avatar.
- Fire Sage Kaja (paternal grandfather)