Shinji Okazaki scored a hat-trick as Japan hammered Saudi Arabia at Al Rayyan Stadium to set up a quarter-final clash with Asian Cup hosts Qatar.
The Stuttgart striker scored twice in the first half before grabbing a late third while Ryoichi Maeda scored a brace to ensure Japan finished top of Group B.
Alberto Zaccheroni's side will tackle Qatar for a place in the semi-finals on Friday.
Japan needed at least a point to be assured of qualification for the last eight but they were clearly hungry for victory and they opened the scoring with just eight minutes on the clock through Okazaki.
Yasuhito Endo spotted the forward's run between the Saudi defence and Okazaki lobbed the keeper before making certain the ball landed in the back net by stabbing home from close range.
It got even better for the Japanese just five minutes later when Okazaki got his second of the game as he was left unmarked inside the area to head home from Shinji Kagawa's cross.
And the win was in no doubt when Japan added a third in the 19th minute when Maeda volleyed home from close range.
Despite their dreadful start, the Saudis finally began to enjoy a spell of possession after that - perhaps due to Japan opting to step down a gear - and they had chances through Osama Al Harbi, Tayseer Al Jassem and Abdullah Suhail.
But normality resumed six minutes into the second half when Maeda headed home his second from a Masahiko Inoha cross.
With no sign of a way back, the Saudi players clearly could not wait for the final whistle to be blown while Japan were seemingly happy to relax and take their foot off the pedal.
But there was time for Okazaki to score his third of the game when he latched onto a pass from Maeda in the 80th minute, worked his way past a couple of defenders before smashing home.
Coach Alberto Zaccheroni believes Japan are getting better with every game. Japan had made a slow start to the tournament with a late Maya Yoshida strike
rescuing a 1-1 draw against Jordan, but they have since gone from strength to
strength with a hard-fought 2-1 win over Syria followed by their rout of the
"I am very satisfied with this result,'' Zaccheroni said. "We have overcome
the first obstacle of the Asian Cup, which was to get through the group stage
and we are improving game by game at this tournament. In any competition we like to get the good results. I was a little worried
about making mistakes but we did not. The players had a great performance.
"Japan is a very young team. I have selected young players. I am very
satisfied with how they have performed and sometimes they play great
Japan will need to maintain their form against a Qatar side that has also been
improving as the Asian Cup has progressed, an observation that was also noted by
"They have come back from their first match defeat and have the momentum,''
he said. "At the same time Japan is in good condition as well so I
expect the next game will be a great match.''
The defeat for Saudi Arabia brings to an end a sorry campaign that has seen the
2007 finalists fail to pick up a single point.
But coach Nasser Al Johar vowed that the Green Falcons will bounce back,
saying: "The Saudi national team is very strong, sometimes we suffer setbacks
but always we recover. I regret what has happened but hopefully the Saudi officials will help us
overcome this and do what needs to be done for the future.''