Trailing 2-0 at half-time after goals from Paulo Henrique and Gabriel Martinelli on Tuesday, hosts Japan capitalised on Brazilian defensive errors before Ueda's late header sealed a famous 3-2 victory in the friendly.
"We couldn't create many chances in the first half, but I sensed there was a chance with (Junya) Ito sending in good crosses. (The goal) feels special," Feyenoord's Ueda told reporters after the win.
"Winning the World Cup is my goal, just like it is for our team. I can't promise it, but we're all developing with that as the target, and I think we're in a position where we can aim for it."
Japan coach Hajime Moriyasu praised his side's performance against the five-time World Cup winners and urged them to keep improving and learning in the buildup to the tournament in the United States, Canada and Mexico.
"We want to fight on the same level, challenge ourselves to see what we can do now and what we lack, and use that to grow. Everyone's hard work led to the result of beating Brazil," Moriyasu said.
"(At half-time) I told my players to put the ball holders under pressure and up their intensity. Winning the World Cup isn't going to be easy, Brazil will up their level at the finals. We'll keep going, taking one step at a time."
Japan, who in March became the first team to qualify for the 2026 World Cup, have reached the round of 16 in three of the last four editions.
In Qatar in 2022, they beat Germany and Spain in the group stage before losing to Croatia on penalties.