Japan suffered a 12-7 defeat to South Korea in its opening round-robin match in the women's curling competition at the Sochi Games on Tuesday.
Japan, who were missing flu-hit Kaho Onodera, took a 2-0 lead in the first end, but the South Koreans pulled level in the second.
After the lead changed hands several times, the South Koreans finally prevailed with five points over the final three ends at Ice Cube Curling Center.
"Our mistakes led to our own downfall," said Japan captain Ayumi Ogasawara. "We'll just have to do better in our next game."
Japan was to play again later in the day against Denmark, while the South Koreans are up against Switzerland.