Substitute Takahiro Sekine made a crucial cameo as he found the net seven minutes after being introduced to settle the fixture, sealing a result that would prove enough to send the club a point clear at the top.
Sagan Tosu had occupied first place, but were held to a shock 1-1 home draw by relegation-zone dwellers Omiya Ardija.
It could have been even worse for Yoon Jung-hwan's men as the visitors moved into a 1-0 lead through Yu Hasegawa four minutes after the break, but Yohei Toyoda came to the rescue with an equaliser seven minutes from time.
Vissel Kobe failed to take advantage of Sagan's unexpected slip-up as they too were held to a 1-1 draw at Shimizu S-Pulse.
The hosts had been without a win in four matches and looked set to fall to a fourth defeat in five when Keijiro Ogawa broke the deadlock shortly after the hour mark.
However, Kota Sugiyama netted five minutes later to deny the visitors three points that would have seen them close the gap between themselves and second to two points.
At the other end of the table, Tokushima Vortis continued to struggle following their promotion via the play-offs and remain stuck on four points from 14 matches after a 1-0 defeat at Kashima Antlers.
Victories for Ventforet Kofu and Yokohama F Marinos over Kashiwa Reysol (3-0) and Kawasaki Frontale (3-0) eased their relegation concerns for the time being, but Gamba Osaka were dragged into the bottom three after a 3-0 defeat to Tokyo.
Elsewhere, Albirex Niigata were held to a 1-1 draw by strugglers Nagoya Grampus, and Vegalta Sendai, who won just one of their opening 10 fixtures, have now won four on the bounce thanks to a 1-0 triumph over Sanfrecce Hiroshima on Sunday.
The competition will now not return until mid-July, with the J.League Cup group stages set to continue in the meantime.
