The reigning champions were three goals to the good inside the opening 20 minutes, while Japan - playing in their first-ever semi-final - had no answer to the early onslaught.
Germany made a dream start scoring in the opening minute as Dzsenifer Marozsan threaded a perfect pass behind the defence for the onrushing Melanie Leupolz to coolly slot home. At 60 seconds, Leupolz’s goal was the fastest at Japan 2012 and the second-quickest over six editions of the tournament.
The margin was doubled by the 13-minute mark as central defender Shiori Kinoshita misjudged a high ball, allowing Marozsan to slip behind the backline and casually lob exposed Japan goalkeeper Sakiko Ikeda. Incredibly, Germany soon extended their lead as Lena Lotzen found space on a corner to power an unstoppable header into the net for her sixth goal of the tournament.
The home side to their credit soon found their feet and the game settled into a more familiar rhythm, with Japan slowly starting to dominate possession. The hosts started the second half with gusto, seeking to make a quick impression and Asuka Nishikawa came close, only to see her effort blocked.
Leupolz grazed the crossbar at the other end with a sharp drive, while Japan continually tried to increase the pressure, causing the German defence moments of panic on several occasions. Most notably, Hanae Shibata went on a stunning mazy run past several would-be tacklers only to scuff her shot wide.
Substitute Ayaka Michigami saw her shot close range shot blocked by a defender as Japan racked up a lengthy list of agonising near-misses. The hosts will now meet Nigeria in the play-off for third on Saturday before USA and Germany do battle for the title.
“We worked together the whole game,” said Germany coach Maren Meinert. “We knew that Japan has a great team and we tried as much we could. The atmosphere was amazing and the fans supported the team for the whole 90 minutes.”
Japan coach Hiroshi Yoshida said: “At the beginning of the game we made some mistakes and Germany scored. That was really tough and my players lost their confidence. Germany played well but we also had some good moments. My team has lot of potential.”