First-half goals from Kohei Shimizu and Hisato Sato put Hiroshima in control and Koji Morisaki's brace after the interval sealed the result, with Yohei Toyoda grabbing a late consolation for the visitors.
All was going to plan for Vegalta when Naoki Sugai put them ahead in the 14th minute in Shimizu, but the hosts hit back and three goals in the final 20 minutes - two from Hyun-Sung Kim and another from Yuji Senuma - turned the game on its head.
Urawa Red Diamonds moved level on points with Vegalta thanks to a 2-1 triumph at Kashiwa Reysol, Popo's last-gasp winner sealing the comeback after Tsukasa Umesaki had cancelled out Mitsuru Nagata's early own goal.
Michael Nascimento scored twice, the first from the penalty spot, as Albirex Niigata stunned Nagoya Grampus Eight 5-0. Takahiro Masukawa's own goal also helped the hosts on their way, with Bruno Lopes and Shusuke Tsubouchi adding gloss to the result in the dying moments.
FC Tokyo edged Jubilo Iwata 2-1, Edmilson and Nemanja Vucicevic grabbing the goals in the second half after Minoru Suganuma's ninth-minute opener.
Leandro's double earned Gamba Osaka a 2-2 draw against Kashima Antlers, twice getting his side back on level terms after goals from Renato and Sergio Dutra.
Renatinho netted the game's only goal 10 minutes from time to earn Kawasaki Frontale a 1-0 home triumph over bottom team Consadole Sapporo.
Cerezo Osaka overturned a two-goal deficit to win 3-2 at Vissel Kobe.
Keijiro Ogawa and Takahito Soma looked to have set the home team on their way to three points with goals in the first 17 minutes, but Fabio Simplicio's double restored parity before Takuma Edamura completed the turnaround nine minutes from time.
Finally, Omiya Ardija and Yokohama F Marinos battled out a goalless draw.