Kei Ikeda's strike seven minutes from time settled the match in Tosu's favour as they went ahead of the Red Diamonds, who needed a last-gasp goal from Daisuke Nasu to draw 2-2 at home to Vissel Kobe.
Shinzo Koroki gave the high-flyers a 17th-minute lead, but Hiroyuki Komoto levelled matters just after the hour before Shunki Takahashi put the visitors ahead after 69 minutes.
Nasu at least rescued a share of the spoils for the Red Diamonds, who have the same points and goal difference as Tosu but have scored one less than their rivals and thus fall to second.
The hosts went in front on the stroke of half-time through Kaoru Takayama and although Kengo Nakamura immediately drew Frontale level, second-half strikes from Masato Fujita, Kaoru Takayama and Montera Leandro settled matters in Reysol's favour.
The Antlers romped to a 5-1 victory over Sanfrecce Hiroshima thanks to goals from Fernandes Caio, Luis Alberto, Daigo Nishi, Davi and Gaku Shibasaki. Sanfrecce had levelled matters through Yoshifumi Kashiwa's goal just before the hour mark but were blown away in the final third of the match.
Rock-bottom Tokushima Vortis had to be content with a 2-2 draw at home to Vantforet Kofu, despite twice taking the lead.
Hiroyuki Takasaki put the strugglers ahead after the half hour mark and although they were pegged back by Naoaki Aoyama, they re-took the lead just before half-time through Yu Eto, only to be denied a third win of the season through Cristiano Da Silva's strike on the hour.
Omiya Ardija also battled back from a goal down to seal a 2-2 draw at Vegalta Sendai. Vegalta took an early lead through Yong Gi Ryang and re-took the lead - after Dragan Mrdja had levelled - thanks to Naoki Ishikawa, but Jiro Kamata's own goal ensured Ardija claimed a hard-fought point.
Goals in the final ten minutes from Patric and Yasuhito Endo helped Gamba Osaka to a 2-0 win over Yokohama F. Marinos, while Sho Naruoka scored four minutes after coming on in the 55th minute to lift Albirex Niigata to a 1-0 success over Cerezo Osaka.