Urawa had racked up back-to-back wins after the mid-season break in Japan's top flight, but were held to a 1-1 draw at home by AFC Champions League hopefuls Kashima Antlers on Sunday.
Shinzo Koroki opened the scoring with his fifth goal of the season in the 20th minute only for Gaku Shibasaki to level the scores on the half-hour mark.
Mihailo Petrovic's men were unable to find a second-half winner at the Saitama Stadium, giving Sagan the chance to cut the lead to just two points at the top of the table.
And they duly delivered three points courtesy of a 1-0 triumph at strugglers Cerezo Osaka, Yohei Toyoda scoring the only goal of the game in the 68th minute.
Kawasaki are a further point adrift in third. Yahiro Kazama's men too triumphed 1-0 at the Kawasaki Todoroki Stadium, Kentaro Moriya grabbing the decisive goal on the hour.
At the bottom of the table, Vortis have endured a miserable campaign and are rooted to the bottom of the league.
But they won for just the second time in the league this season thanks to a 3-1 victory at 17th-placed Omiya Ardija, who are yet to win since returning to action.
Hiroyuki Takasaki scored a brace either side of Zlatan Ljubijankic's leveller, before Yu Eto made sure of the points for the visitors in the second half to ensure Tokushima's first maximum haul since the end of April.
Fellow strugglers Ventforet Kofu and Nagoya Grampus drew their respective fixtures with Sanfrecce Hiroshima and Yokohama F Marinos 1-1, while Shimizu S-Pulse and Tokyo were 3-0 winners in their home matches with Kashiwa Reysol and Vegalta Sendai.
Rounding off the action, Takashi Usami and Patric both scored twice as Gamba Osaka thumped Vissel Kobe 5-1 on their trip to the Noevir Stadium Kobe.