Midfielders Takuya Nozawa and Mitsuo Ogasawara hit first-half goals for Kashima who took advantage of FC Tokyo's 1-0 defeat at Nagoya Grampus Eight to take the outright lead.
Kashima have 13 points from five matches with FC Tokyo and Yokohama F-Marinos on 10.
Nagoya Grampus Eight keeper Seigo Narazaki saved an early penalty from Lucas and the hosts bagged the points through Brazilian striker Marques in the second half.
Last year's second-stage winners Urawa Reds still await their first win after a 1-1 draw at home to Shimizu S-Pulse. A Cho Jae Jin header put the visitors in front before midfielder Makoto Hasebe replied with a well-worked goal two minutes before halftime.
JEF United won their second game in five days cruising to a 3-1 victory at Jubilo Iwata. Mario Haas set up first half goals for Yuto Sato and Daisuke Saito.
In other matches Korean Ahn Jung Hwan netted the winner as champions Yokohama F-Marinos edged Kashiwa Reysol 1-0 while Tokyo Verdy managed by Argentine Ossie Ardiles were thrashed 4-1 by Sanfrecce Hiroshima.