Akimi Barada scored in the 63rd minute as rock-bottom Omiya Ardija stunned J. League-leading local rivals Urawa Reds with a 1-0 win on Sunday.
Ardija went into the match at Nack 5 Stadium having endured a dreadful start to the season, losing seven and drawing one of their eight league games and managing to score only two goals while conceding 17.
Omiya's record stood in stark contrast to the imperious form of last season's championship runner-up Urawa, which started the day four points clear at the top of the table after scoring 24 goals in eight games.