Japan's midfielder Ritsu Doan scores the penalty kick for the opening goal during the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
DUBAI, United Arab Emirates (AP) - Four-time champion Japan was first into the Asian Cup semifinals after beating Vietnam 1-0 on Thursday.
Midfielder Ritsu Doan converted from the penalty spot with a low left-foot shot in the 57th minute of the quarterfinal.
It was Japan's fifth win in five games, all by a one-goal margin.
Japan faces Iran or China in the semifinals.
VAR was introduced at the Asian Cup on Thursday for the rest of the tournament, and disallowed a first-half goal by Japan captain Maya Yoshida. VAR revealed the ball hit his arm.
Rebuilding the team that reached the World Cup last 16, coach Hajime Moriyasu has proved effective in helping Japan win its Group F before knocking out Saudi Arabia 1-0 in the round of 16.
Outsider Vietnam made the knockout stage only as the last, fourth best third-placed team. It knocked out Jordan in a penalty shootout.
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Japan's midfielder Ritsu Doan, centre, is fouled during the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
Japan players celebrate the opening goal during the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
Japan's forward Koya Kitagawa, right, goes for the ball past Vietnam's defender Bui Then Dungi during the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
Vietnam's soccer team supporter holds a traditional hat ahead of the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
Japan's midfielder Ritsu Doan controls the ball past Vietnam's midfielder Do Hung Dung during the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
Japan's midfielder Ritsu Doan goes for the ball with Vietnam's defender Doan Van Hau during the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
Japan's soccer team supporters smile ahead of the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
Japan's head coach Hajime Moriyasu ahead of the the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
Vietnam's soccer team supporters cheer ahead of the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press
Japan's defender Maya Yoshida controls the ball during the AFC Asian Cup quarterfinal soccer match between Japan and Vietnam at Al Maktoum Stadium in Dubai, United Arab Emirates, Thursday, Jan. 24, 2019. (AP Photo/Hassan Ammar)
The Associated Press