Yang (left) and Zhang disappointed the home fans
Chinese top seeds Yang Wei and Zhang Jiewen suffered an upset in the women's doubles badminton quarter-finals.
Unseeded Japanese duo Maeda Miyuki and Suetsuna Satoko rallied from near defeat to eliminate the defending Olympic champions in Beijing.
The Chinese had two points to win the match at 19-16 in the second game, but lost it 23-21 after a series of errors.
Clearly rattled, they crumbled in the second half of game three, giving up 12 of the final 17 points to lose 14-21.
"This was the biggest win of our lives," said Suetsuna.
"They are the Olympic champions so even when we had 20 points in the third game we couldn't take anything for granted.
"It wasn't until we got that final point that we could celebrate."