Japan defeated Argentina 1-0 for the first time in a friendly on Friday and posted its first win under new coach Alberto Zaccheroni.
Striker Shinji Okazaki pounced on the rebound of Argentina goalkeeper Romero's save from Makoto Hasebe's shot in the 19th minute.
"I'm very happy," Zaccheroni said. "It was an important match especially given the opponents we were facing. I told my players before the game that if they believed, they could do it."
Argentina was at full-strength with a lineup including Lionel Messi, Carlos Tevez and Diego Milito, but it created few good scoring chances and never really found a rhythm in the face of solid Japan defending.
Japan, which last faced Argentina in an August 2004 friendly, had lost all six previous games against the South Americans.
The win was Japan's first against a team ranked inside the world's top 10 since April 2004, when Zico's side beat the Czech Republic 1-0 in a friendly.
The 57-year-old Zaccheroni replaced Takeshi Okada, who stepped down as coach after leading Japan to the second round of the World Cup in June.
Interim Argentina coach Sergio Batista suffered his first loss since replacing Diego Maradona following the World Cup.
Batista oversaw a 1-0 win against Ireland and a 4-1 win over world champion Spain.
