Omiya Ardija denied local rivals Urawa Reds the chance to move into second in the table after a surprise 2-1 away win in the J. League first division on Saturday.
First-half goals from Brazilian midfielder Toninho and Naoto Sakurai settled the Saitama derby while the result saw last season's league runnerup Urawa slip 12 points behind leaders Kashima Antlers, who defeated Kawasaki Frontale 2-0 at home.
Kashima bounced back from its midweek defeat at Yokohama F. Marinos thanks to an own goal and a trademark free-kick from Mitsuo Ogasawara in a bad-tempered match that saw nine players booked.
Kashima leads the table on 35 points from 15 games, 10 clear of Gamba Osaka, which hosts struggling Kashiwa Reysol on Sunday.