Germany needed an injury-time winner from substitute Lina Magull to subdue a resolute Ghana and secure a 1-0 win in their Group D contest in Hiroshima.
USA's draw later in the evening against China PR, leaves Germany in a position to lock up top spot in the group with just a point against the Stars and Stripes in Monday's final round.
Germany had the better of the contest but the Africans battled hard throughout, only for Magull to profit from a perfect Dzsenifer Marozsan pass and score the all-important goal just eight minutes after entering the fray.
Germany restricted the hard-working Ghana side to few openings, while at the other end the reigning champions came close on several occasions.
Ghana made three changes to the side which were beaten 4-0 by USA in the opener, and it was a much-improved performance from the Black Princesses.
A Luisa Wensing header forced a great save from Ghana goalkeeper Patricia Mantey early on, while at the other end, Florence Dadson’s effort required an equally impressive stop from Germany custodian Laura Benkarth.
The champions soon started to assert their authority and Nicole Rolser twice, and Lena Lotzen, came close to breaking the deadlock before the interval.
Mantey was inspired form after the break making several important stops, notably denying Leonie Maier, however the goalkeeper’s heroics were to no avail thanks to Magull’s late intervention.
“Ghana played well, they are very athletic and there is no comparison to the game before against China,” said Germany coach Maren Meinert.