Japan had to settle for a share of the spoils in its final warmup before leaving for Germany for the Women's World Cup on Saturday after gifting South Korea an equalizer in a 1-1 draw.
Midfielder Aya Miyama fired Japan in front midway through the second half in atrocious playing conditions, but sloppy defending allowed Japan-based striker Ji So Yun to snatch a 75th minute leveler for the visitors.
Japan meets New Zealand on June 27 in Bochum in its opening match in a Group B that also features England and Mexico.
"We were hoping to get a win to take with us before we play our opener against New Zealand but had to settle for a draw after giving that goal away," said Japan coach Norio Sasaki.
"Still, we kept trying to score until the end and it wasn't easy because we couldn't train in these (wet) conditions. There were things that didn't quite go the way we wanted but the players still tried hard and battled for the ball."