Coach Hajime Moriyasu said Japan can become the best in the world after beating Brazil for a second time, as he prepares to step down after eight years in charge.
Japan shocked the five-times world champions 3-2 in a friendly in Singapore on Saturday, with substitute Tatsuhiro Sakamoto scoring an injury-time winner.
The victory came just more than a year after Japan beat Brazil for the first time in a friendly in Tokyo.
Brazil eliminated Japan from this year's World Cup in North America with a 2-1 win in the last 32.
Moriyasu will leave his job after a friendly against Paraguay on Tuesday but he is certain that Japan are on track to become a major football nation.
"The players showed confidence and courage and dug in when they needed to dig in," he said.
"At the World Cup in the future, Japan can absolutely become the world's best."
Moriyasu, Japan's longest-serving coach, was originally set to lead the team at the Asian Cup in Saudi Arabia in January before handing the reins to current Under-23 boss Go Oiwa.
But the Asian Football Confederation announced that the tournament would be pushed back to December 2027 due to "exceptional circumstances" in the region, following Houthi attacks on the host country.
The JFA confirmed on Friday that next week's game would be Moriyasu's last.
"Aiming for wins and growth, I will strive to do my best as I always have," Moriyasu said.
Japan were looking for revenge after a heart-breaking loss to Brazil at the World Cup.
Gabriel Martinelli scored in the 95th minute in Houston to send Brazil through.
Japan midfielder Ao Tanaka, who was in floods of tears after making a late mistake in the World Cup game, said after the win in Singapore that he was "calm but really happy".
"All sorts of things started coming back to me as the game got closer, and of course those frustrating memories were in my head," said the Leeds United midfielder.
Japan took an early 2-0 lead before Brazil hit back through two Vinicius Junior wonder strikes.
Coventry winger Sakamoto won it for Japan in injury time, before Brazil coach Carlo Ancelotti and captain Raphinha were sent off for protesting the goal.
The 30-year-old Sakamoto was making his first Japan appearance for five years.
"To come back like this and make a contribution in such a massive match, one we all really wanted to win, gives me so much confidence," said Sakamoto.
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