Jason Shimura was the oldest son of Cornelius and Phyllis Shimura, and the brother of Brett. He died under mysterious circumstances prior to the start of the series. It has affected the big picture of the series. This made Troy Bolton take the decision to become a detective so he could investigate the mystery behind Jason's death.
As Jason was killed prior to the start of the series, not much information about his personality is known. According to Brett, he was the best brother anyone could've asked for, and was a genuinely nice person who didn't deserve to die. Jason was very protective of his loved-ones, especially Brett.
Despite his death, Jason's actions still has a GREAT effect on his younger brother, as his love and affection on him made it possible for Brett to have peace with someone. Brett is also haunted by Jason psychologically as well, consistently having dreams of Jason’s corpse attacking him, almost killing him. Brett himself would go on to feel he was gradually becoming like someone else as the series progresses.
- Even after death, Jason Shimura's impact on Brett's life still lives on as depicted in his dreams.